After looking at what water baptism was in the first century, I will look at what is has become in all succeeding centuries.
From the time John the Baptist and Jesus’ apostles first administered water baptism until the Day of Wrath and Salvation only approximately 40 years would pass. Water baptism had a fixed design and terminus. It declared deliverance from the coming wrath and salvation in the coming new day for all who were so appointed by God. Both of these truths are revealed in baptism's original setting in the narratives of Jesus (the "Gospels") and in its interpretation by Peter in his first letter.
Baptism first appears in Matthew through John the Baptist. "Now in those days John the Baptist came, preaching in the wilderness of Judea, saying, 'Repent, for the kingdom of heaven is at hand'"... "Then Jerusalem was going out to him, and all Judea, and all the district around the Jordan; and they were being baptized by him in the Jordan River, as they confessed their sins. But when he saw many of the Pharisees and Sadducees coming for his baptism, he said to them, 'You brood of vipers, who warned you to flee from the wrath to come? Therefore bear fruit in keeping with repentance; and do not suppose that you can say to yourselves, ‘We have Abraham for our father’; for I say to you that from these stones God is able to raise up children to Abraham. And the axe is already laid at the root of the trees; therefore every tree that does not bear good fruit is cut down and thrown into the fire." Clearly, the application was about deliverance from the Day of the Wrath of God. Baptism was the applied symbol to the repentant people - the followers of Jesus.
This reality was underscored by Peter when he interpreted baptism for his gentile letter recipients. "For Christ also suffered for sins once for all, the righteous for the unrighteous, so that He might bring us to God, having been put to death in the flesh, but made alive in the spirit, in which also He went and made proclamation to the spirits in prison, who were disobedient when the patience of God was waiting in the days of Noah during the preparation of the ark, in which a few, that is, eight persons were saved through water - which the figure of baptism now is saving us, not the removal of dirt from the flesh, but an appeal of a good conscience to God through the resurrection of Jesus Christ, who is at the right hand of God, having gone into heaven, after angels and authorities and powers had been subjected to Him." Most Bible translations wrongly translate the comparison of the water of the flood to baptism. They make it say the water of the flood is that which corresponds to, that is, typifies baptism which saves when added to a good conscience. Except for the appeal of a good conscience, the exact opposite was Peter's teaching. He taught that baptism was the corresponding type, the figure of salvation that saved from judgment. In the flood, it was not the water that saved Noah and his family. It was the ark through their submission to God. In the Day of Wrath, it was not baptism that saved from judgment - that was the predetermined type - it was Jesus. Noah and his family heard God and built and entered the ark for salvation. The people of God heard John, and then Jesus and repented from their sins for salvation. Peter stressed, refined, and defined the truth by telling his letter recipients that it was not the actual water on the body that saved, but their "appeal of a good conscience to God through the resurrection of Jesus Christ".
It was Paul who in his letter to the Roman believers developed the application of baptism to signify in one act burial with Jesus joined to resurrection with Him. Indeed, the repentance called for by John the Baptist and Jesus, his heralded Lord, was prefigured by baptism in death to sins and life to God through Jesus. Baptism was the God-appointed means to declare those facts in the very same way that circumcision declared that Jews under Moses were the covenanted-submissive people of God. Circumcision did not make them submissive. It was sign that they were submissive. Paul said that very thing in the same letter just referred to when he said of Abraham, "and he received the sign of circumcision, a seal of the righteousness of the faith which he had while uncircumcised, so that he might be the father of all who believe without being circumcised, that righteousness might be counted to them".
The spiritual perception is highly lacking today, it is all but gone, that Jesus Christ is shown in the Scriptures to be the juxtaposed fulfillment of Moses in very many things. This case of baptism in the Name of Jesus is one of those many cases.
Baptism was prefigured as a type of salvation. It was not the reality as types are not the realities that they typify. The word that Silas (Peter's secretary) used was antitypos. It was used twice in the New Covenant Scriptures. Aside from this usage, the author of Hebrews used it to say that the tabernacle of Moses was itself a symbol - an antitypos - of the true tabernacle of Heaven, the spiritual dwelling of God.
In summary, baptism was the badge and pledge of the righteous, showing their discipleship to Jesus the Messiah and Savior, and at the same time declaring their deliverance from the coming Day of Wrath and their participation in the coming Day of Salvation. That Day of Wrath has been fulfilled. That Day of Salvation has come. Baptism has fulfilled its purpose. To continue to practice water baptism is not to understand its God-appointed function as developed by John the Baptist, Jesus, and Paul.
What, then, is water baptism now? How is it interpreted?
Because baptism was never properly understood by the Patristic Churches as the sign put for the substance, declaring to the last generation of the Mosaic Law that both deliverance from God's wrath and salvation in His Kingdom through Jesus was near, it was turned into something that is never was. It was pressed into the essential service of justification by faith in the sight of God. Later, standard misinterpretation pressed it into the service of simple church membership and as the timeless sign of discipleship.
Before John the Baptizer appeared, there is no mention of this practice in the Scriptures. There was, however, a very substantial historical backdrop to his ministry. The Essenes and especially the Qumran Community practiced water baptisms as part of their purification rites. The Qumran sect did so on a daily basis. It is highly likely that John interacted with the Qumran sect before his public appearance. Be that as it may, if he did, there was a huge difference between his baptism and theirs. As stated, theirs was continual on a daily basis and, they believed, secured their purification before God. John’s was a one time event and bound the new people of God as identified with their Deliverer and Purifier Jesus, the Messiah of Israel.
Without the ground of proper understanding, the Patristic Churches immediately saw water baptism as an essential part of justification before God. They misinterpreted the entire significance of baptism and made that last days sign of submission to Jesus into the required act which became the cooperative ground of justification. They made it into a timeless ordinance of command for everyone who would be a Christian. It has stood among many as such to this day! For those who reject the regenerational aspect of water baptism, but who have retained its authority as the timeless required badge of church membership or discipleship to Jesus, the anachronistic practice remains.
Read my short note under the link "Church Ordinances" for an overview of the current status of water baptism.
Also, read my essay under the link "The one and only assembly council" where this subject is dealt with.