Let's look at the verse in context:
[SUP]"18 [/SUP]For Christ also hath once suffered for sins, the just for the unjust, that he might bring us to God, being put to death in the flesh, but quickened by the Spirit:[SUP]19 [/SUP]By which also he went and preached unto the spirits in prison;
[SUP]20 [/SUP]Which sometime were disobedient, when once the longsuffering of God waited in the days of Noah, while the ark was a preparing, wherein few, that is, eight souls were saved by water.
[SUP]21 [/SUP]The like figure whereunto even baptism doth also now save us (not the putting away of the filth of the flesh, but the answer of a good conscience toward God,) by the resurrection of Jesus Christ:
[SUP]22 [/SUP]Who is gone into heaven, and is on the right hand of God; angels and authorities and powers being made subject unto him."
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The meaning of the passage is this: The Lord Jesus Christ died, was buried and resurrected. That was His Baptism. In the time of His death, He descended into the lower parts of the Earth or Hades and preached to the disobedient spirits there. Those were the same spirits who sinned prior to the flood. Peter then references the flood and the ark, specifically, which was a foreshadow of Jesus Christ in the sense of its salvation. It is also a forehsadow of water baptism which is an antetype of the death, burial and resurrection of our Lord.
So the "baptism" in verse 21 is the baptism of Christ, which indeed saves us from sin.
Our Lord confirmed this Himself:
"[/SUP] [SUP]21 [/SUP]And he said unto her, What wilt thou? She saith unto him, Grant that these my two sons may sit, the one on thy right hand, and the other on the left, in thy kingdom.
[SUP]22 [/SUP]But Jesus answered and said, Ye know not what ye ask. Are ye able to drink of the cup that I shall drink of, and to be baptized with the baptism that I am baptized with? They say unto him, We are able.
[SUP]23 [/SUP]And he saith unto them, Ye shall drink indeed of my cup, and be baptized with the baptism that I am baptized with: but to sit on my right hand, and on my left, is not mine to give, but it shall be given to them for whom it is prepared of my Father." - Matthew 20
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The Baptism being referred to here is DEATH. And that is the baptism Peter is speaking of. Because Christ's death and resurrection, or His "baptism" indeed saves us who believe in the Biblical Gospel.[/SUP]