1 Peter 3:21

Verse 21. The like figure whereunto even baptism.

The saving of Noah and family by water, Peter says, is a figure of baptism, which he affirms doth also now save us. God saved Noah by water because he believed and obeyed God, and destroyed all others then living, because they believed not, and of course refused to obey. That was his appointment then. "He that believeth and is baptized shall be saved" (Mark 16:16) is God's appointment now. Complying with God's appointment in baptism, we are safe; or baptism, the antitype of the waters of the flood, saves us. The prerogative is with God to name the conditions or means, and on the part of his creatures to accept. Comply and be saved, or reject and be destroyed.

Answer of a good conscience.

Toward God the answer of the conscience is good whenever our own consciousness assure us that we have done just what God required of us, without alteration or substitution. We mistake not when we take God at his word. Anything less leads to danger. And as if inspiration looking down the ages by anticipation would guard against all mistakes, utters its warning. Inspiration saw in the future partisan zeal, claiming that as the water of baptism only affected the body, it was unnecessary; that the office of baptism was to wash the body simply. The Spirit in Peter says this is a mistake. It is not commanded for that purpose at all, but for the answer of a good conscience. God commands baptism. Man complying has a conscience in that respect void of offense. His conscience is good. It could not have been good had he failed to obey the command. The mistake as to the office-work of baptism might occur, because the whole body is washed, but how on earth a mistake could occur as to its form, no one can rationally tell. The whole body enveloped in water is as far removed in action from any form of affusion as day is from night.

By the resurrection of Jesus Christ.

God demonstrated to the world the Messiahship of Jesus by raising him from the dead. He was determined by that resurrection to be God's Son, and clothed with all authority in heaven and on earth. He it is who commands baptism. It is his appointment. By it he saves. He had the power to have suspended salvation upon some other terms, or upon something else, but he did not, and that is the end of the matter. We can not question his authority, and it is impious to doubt his ability and willingness.