Christ said this:

Go into all the world and preach the gospel to every creature. He who believes and is baptized, will be saved; but he who does not believe will be condemned (Mark 16:15-16 NKJV, emphasis added).

It is not enough to just believe the Gospel. We must live it, as we can see in Matthew 7:21-23 NKJV:

Not everyone who says to Me, 'Lord, Lord,' shall enter into the kingdom of heaven, but he that doeth the will of My Father in heaven. Many will say to Me in that day, 'Lord, Lord, have we not prophesied in Your name, cast out demons in Your name, and in Your name done many wonders?' And then I will declare to them, 'I never knew you; depart from Me, you who practice lawlessness!'

Those referred to in the above passage profess faith in Jesus. They preached in His name, and even claim to have done great works in His name, but they don't keep the law. Lawlessness is the only definition of sin in Scripture:

Whoever commits sin also commits lawlessness, and sin is lawlessness (1 John 3:4 NKJV).

Obedience is the fruit of a relationship with God. Understanding the character of God, His love, and His care for all creation is vital if we wish to understand the demands of the law. If we love God, we will wish to keep the law because God's love for us is embodied in the law:

The law of the LORD is perfect, converting the soul: the testimony of the LORD is sure, making wise the simple. The statutes of the LORD are right, rejoicing the heart: the commandment of the LORD is pure, enlightening to the eyes. The fear of the LORD is clean, enduring for ever: the judgments of the LORD are true and righteous altogether. More to be desired are they than gold, yea, than much fine gold: sweeter also than honey and the honeycomb. Moreover by them is thy servant warned: and in keeping of them there is great reward (Psalm 19:7-11).

It is not enough to have a theoretical knowledge of the law. Keeping the law just because we know it is right is legalism. The law must be kept from the heart. It must become part of our character. Only then will we be able to reflect the love of Christ to a world in need.

For not the hearers of the law are just before God, but the doers of the law shall be justified (Romans 2:13).

If ye love me, keep my commandments (John 14:15).

Returning to Mark 16:16—"He who believes and is baptized, will be saved"—we can now understand the full significance of the word "baptized.” Baptism is the symbol of the changed life. It is the symbol of rebirth, a demonstration of the death of the old sinful person and the resurrection of the transformed person, who lives in harmony with the law of God. Baptism is the symbol of restoration.

And be not conformed to this world: but be ye transformed by the renewing of your mind, that you may prove what is that good, and acceptable, and perfect, will of God (Romans 12:2).

Until we are touched by God’s grace and the workings of His Spirit, it is impossible to obey Him. It is the Spirit of God that enables us to live in harmony with the will of God.

Because the carnal mind is enmity against God: for it is not subject to the law of God, neither indeed can be. So then they that are in the flesh cannot please God (Romans 8:7-8).

In John 3, Jesus discusses the nature of the spiritual rebirth with Nicodemus. In verse 5 He says this:

Most assuredly, I say to you, unless one is born of water and the Spirit, he cannot enter the kingdom of God (John 3:5, NKJV).

The Holy Spirit works inside us to transform us into people who reflect the character of Jesus. The water—baptism—is the outward symbol of our willingness to accept the transformation process. Obedience to God comes as a gift from God.

Both justification and sanctification are gifts we receive through faith in the Son of God. Justification is the legal side of our relationship with God. We are declared innocent, even though we are guilty, because Christ paid the penalty for our sins. Sanctification is the active side of our relationship with God. It is the little-by-little, daily process of the Holy Spirit making us more like Him.

We did nothing to deserve either of these gifts. Our job is to accept them.

...he saved us, not because of righteous things we had done, but because of his mercy. He saved us through the washing of rebirth and renewal by the Holy Spirit (Titus 3:5 NIV).

Justification and sanctification are a package deal. Refusal to accept sanctification is a demonstration of false justification:

Wherefore by their fruits, ye shall know them (Matthew 7:20).

Baptism is the outward sign that we accept God’s offer of justification and sanctification. We accept the invitation into a covenant relationship with God, the new covenant that God promised to spiritual Israel:

Behold, the days come, saith the Lord, that I will make a new covenant with the house of Israel and with the house of Judah; not according to the covenant that I made with their fathers in the day that I took them by the hand to bring them out of the land of Egypt, which My covenant they brake, although I was a husband unto them, saith the Lord. But this shall be the covenant that I will make with the house of Israel after those days, saith the Lord: I will put My law in their inward parts, and write it in their hearts; and I will be their God, and they shall be My people (Jeremiah 31:31-33 emphasis added).

Baptism is the outward symbol of rebirth, but is also the outward sign of entrance into the body of Christ—His Church.

For by one Spirit are we all baptized into one body, whether we be Jews or Gentiles, whether we be bond or free; and have been all made to drink into one Spirit...ye are the body of Christ (1 Corinthians 12:13,27).

A teenager hugs her mom after being baptized in the ocean.
Source: eren on Flickr....

Those who accept Jesus are not just choosing to follow Him by themselves. Following Christ means becoming part of the Church.

If by being baptized we demonstrate our acceptance of the covenant relationship with God, then we also become a part of the covenant people of God.

So we, being many, are one body in Christ, and every one members of one another (Romans 12:5, see also 1 Corinthians 10:17; Colossians 3:15).

For as the body is one and hath many members, and all the members of that one body, being many, are one body, so also is Christ. For by one Spirit are we all baptized into one body…For the body is not one member by many. But now are they many members, yea but one body (1 Corinthians 12:12-14, 20).

There is one body and one Spirit, even as ye are called in one hope of your calling (Ephesians 4:4).

The true body of Christ teaches obedience to God's commands and has faith in the transforming power of the Holy Spirit. One cannot be baptized and live apart from the Church. That would be like an organ trying to exist outside the body.

God has always worked through His organized Body, the Church. Even Christ worked within the organized Body of that era: the people of Israel.

When we are baptized, we enter into a covenant relationship with God. The promises He made to His people become applicable to us. One of those promises is the gift of the Holy Spirit.

Jesus—who Himself had the Holy Spirit descend on Him upon baptism (see Matthew 3:16-17 and Mark 1:4-12)—promised that we would receive the Holy Spirit to comfort and to guide us:

If ye love Me, keep My commandments. And I will pray the Father, and He shall give you another comforter, that He may abide with you forever - the Spirit of truth, whom the world cannot receive, because it seeth Him not, neither knoweth Him; but ye know Him, for He dwells with you, and shall be in you (John 14:15-17).

And Peter, after receiving the Holy Spirit himself, reminded the people of God’s promise:

Repent, and let every one of you be baptized in the name of Jesus Christ for the remission of sins; and you shall receive the gift of the Holy Spirit. For the promise is to you and to your children, and to all who are afar off, as many as the Lord our God will call (Acts 2:38-39 NKJV).

The promise of the Holy Spirit is given to those who believe and are baptized. It is conditional to repentance and obedience.

...the Holy Spirit whom God hath given to them that obey Him (Acts 5:32 emphasis added).

Know ye not, that so many of us as were baptized into Jesus Christ were baptized into his death? Therefore we are buried with him by baptism into death: that like as Christ was raised up from the dead by the glory of the Father, even so we also should walk in newness of life (Romans 6:3-4 emphasis added).

Even the ability to repent and obey is a gift from God. It is the Holy Spirit Himself who is sent to “convict the world of sin, and of righteousness, and of judgment” (John 16:8 NKJV). So baptism is not just accepting the forgiveness of Jesus, it is accepting the transforming power of Jesus to help us repent and obey in the first place. In baptism, "our old man is crucified with him, that the body of sin might be destroyed, that henceforth we should not serve sin" (Romans 6:6).

Baptism is the sign of the death of our selfish, sinful nature. That old, worldly person is buried in the waters of baptism.

A baptism by immersion is celebrated in the Philippines.
Source: David Quitoriano on Flickr....

And those who are Christ's have crucified the flesh with its passions and desires. If we live in the Spirit, let us also walk in the Spirit (Galatians 5:24-25 NKJV).

Know ye not, that so many of us as were baptized into Jesus Christ were baptized into his death? Therefore we are buried with him by baptism into death: that like as Christ was raised up from the dead by the glory of the Father, even so we also should walk in newness of life...Knowing this, that our old man was crucified with him, that the body of sin might be destroyed, that henceforth we should not serve sin (Romans 6:3-6).

Baptism is the beginning of a new life with God. The Holy Spirit makes us clean and gives us a new identity and purpose:

Not by works of righteousness which we have done, but according to His mercy He saved us, through the washing of regeneration and renewing of the Holy Spirit (Titus 3:5 NKJV).

For the sinful nature desires what is contrary to the Spirit, and the Spirit what is contrary to the sinful nature. They are in conflict with each other, so that you do not do what you want...But the fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness, gentleness and self-control. Against such things there is no law (Galatians 5:17,22-23 NIV).

The Holy Spirit prepares us for our new occupation as His servant and new identity as His child (see John 14:17, 26 and 1 John 3:1-3). He imparts His gifts of service that we are to use to spread the Gospel. These gifts are listed in Romans 12:6-8; 1 Corinthians 12:8-11,28,31; and Ephesians 4:11-12. Read more about the spiritual gifts

Some say that we should take Sunday as our day of worship in order to celebrate Christ's resurrection. However, we already have such a celebration: baptism.

The seventh-day Sabbath was instituted to commemorate Creation (Exodus 20:8-11; 31:17). It also served as a reminder of God's restoring and saving work in our lives—a reminder that these things cannot be accomplished through our own works (Exodus 31:13; Hebrews 4:10). We rest on the seventh day to honor our Creator and our Saviour. However, many Christians defend Sunday as the day for worship on the grounds that they are celebrating Christ's resurrection from the grave after His death on the cross.

When we consider Christ's resurrection from the dead, we must realize that it was possible only because of His sinless life. Because He had not sinned once during his entire life on this earth, Christ was not defeated by Satan, and was able to rise again from the death on the cross. Death could not hold Him because He was unconquered by the Enemy. The way we celebrate Christ's resurrection is by participating in the rite of baptism.

Baptism is, among other things, our own participation in Christ's death, and our own resurrection to a new life in Christ. When we are submersed under the water, it is a sign that we are choosing to let our old life die. And when we rise from the water that symbolizes a watery grave, we are choosing and receiving on a daily basis a new life in Christ—trusting in the merits of Christ to save us, and choosing to daily slay the old selfish desires that fight against Christ's principles. The new birth experience celebrates Christ's resurrection by applying the power of His resurrection to our lives through our own choice.

When Christ was baptized by John the Baptist, He was not declaring Himself a sinner that needed to be saved. He was baptized as an example for us to follow, and as a substitute for those who have, for one reason or another, been unable to demonstrate their choice to follow Jesus through the rite of baptism. Perhaps they were invalid, on their deathbed, or simply far away from any other Christian that could assist them in this rite. In those cases, Jesus Christ was baptized on their behalf. But for us who are able to freely make the decision to live for Christ it is a privilege and a duty.