The following is an excerpt from The MacArthur New Testament Commentary on 1 Peter 3.

Corresponding to that, baptism now saves you—not the removal of dirt from the flesh, but an appeal to God for a good conscience—through the resurrection of Jesus Christ, (3:21)

Peter used corresponding to that, a phrase containing the word antitupon, which means “copy,” “counterpart,” or “figure pointing to” to make the transition to the salvation in Christ. That word yielded the theological term antitype, which in the New Testament describes an earthly expression of a heavenly reality—a symbol or analogy of a spiritual truth (cf. John 3:14–16; Heb. 4:1–10; 8:2, 5). The preservation in the ark of those who believed God is analogous to the salvation believers have in Christ.

Some commentators believe the Flood is the antitype because antitupon (v. 21) and hudatos (water, v. 20) are both neuter nouns. But it is better to view the antitype in the broader sense of Noah and his family’s total experience with the ark. God preserved them from the flood waters while the rest of mankind perished. Noah and his children are a genuine type of the salvation in Jesus Christ, which preserves believers safely through God’s judgment on sinners.

Certain theological traditions misinterpret Peter’s statement baptism now saves you to refer to spiritual salvation by water baptism (i.e., baptismal regeneration). But baptism (from baptizo) simply means “to immerse,” and not just in water. Peter here uses baptism to refer to a figurative immersion into Christ as the ark of safety that will sail over the holocaust of judgment on the wicked. Noah and his family were immersed not just in water, but in the world under divine judgment. All the while they were protected by being in the ark. God preserved them in the midst of His judgment, which is what He also does for all those who trust in Christ. God’s final judgment will bring fire and fury on the world, destroying the entire universe (cf. 2 Peter 3:10–12); but the people of God will be protected and taken into the eternal new heavens and new earth (v. 13).

Peter made clear that he did not want readers to think he was referring to water baptism when he specifically said not the removal of dirt from the flesh. (For a more complete discussion of baptism and regeneration, see John MacArthur, Acts 1–12, MacArthur New Testament Commentary [Chicago: Moody, 1994], 73–75.) That he was actually referring to a spiritual reality when he wrote baptism now saves is also clear from the phrase, an appeal to God for a good conscience—through the resurrection of Jesus Christ. The only baptism that saves people is dry—the spiritual one into the death as well as the resurrection of Christ—of those who appeal to God to place them into the spiritual ark of salvation safety (cf. Rom. 10:9–10).

Just as the Flood immersed all people in the judgment of God, yet some passed through safely, so also His final judgment will involve everyone, but those who are in Christ will pass through securely. The experience of Noah’s family in the Flood is also analogous to the experience of everyone who receives salvation. Just as they died to their previous world when they entered the ark and subsequently experienced a resurrection of sorts when they exited the ark to a new post-Flood world, so all Christians die to their old world when they enter the body of Christ (Rom. 7:4–6; Gal. 2:19–20; Eph. 4:20–24). They subsequently enjoy newness of life that culminates one day with the resurrection to eternal life. Paul instructed the Romans:  Or do you not know that all of us who have been baptized into Christ Jesus have been baptized into His death? Therefore we have been buried with Him through baptism into death, so that as Christ was raised from the dead through the glory of the Father, so we too might walk in newness of life. (Rom. 6:3–4; cf. 1 Cor. 6:17; 10:2; 12:13; Gal. 3:27; Eph. 4:5)Therefore, God provides salvation because a sinner, by faith, is immersed into Christ’s death and resurrection and becomes His own through that spiritual union. Salvation does not occur by means of any rite, including water baptism (the removal of dirt from the flesh), but by an appeal to God for a good conscience. Appeal (eperotema) is a technical term that was used in making contracts. Here it refers to agreeing to meet certain divinely-required conditions before God places one into the ark of safety (Christ). Anyone who would be saved must first come to God with a desire to obtain a good (cleansed) conscience and a willingness to meet the conditions (repentance and faith) necessary to obtain it. By appealing to God for a good conscience, that is, a conscience free from accusation and condemnation (cf. Rom. 2:15), the unregenerate show that they are tired of the sin that dominates them and desire to be delivered from its burden of guilt and the threat of hell (cf. Luke 18:13–14; Acts 2:37–38). They crave the spiritual cleansing that comes through Christ’s shed blood (3:18; cf. 1:18–19; 2:24; Heb. 9:14; 10:22). Therefore they repent of their sins and plead for God’s forgiveness and the removal of the guilt that plagues their consciences, all of which is available through trusting in the atoning sacrifice of Christ. Water baptism does not save; it is the Holy Spirit’s baptizing the sinner safely into Jesus Christ—the elect’s only ark of salvation—that forever rescues the sinner from hell and brings him securely to heaven. This is the ultimate triumph of Christ’s suffering for them, and the pledge of triumph in their own unjust suffering.