Adam Clarke's Commentary on the Bible

Verse 21 (1 Peter 3:21)

The like figure whereunto, etc. - Dr. Macknight has translated this verse so as to make the meaning more clear: By which (water) the antitype baptism (not the putting away of the filth of the flesh, but the answer of a good conscience towards God) now saveth us also, through the resurrection of Jesus Christ.

He remarks that the relative ᾡ being in the neuter gender, its antecedent cannot be κιβωτος , the ark, which is feminine, but ὑδωρ , water, which is neuter.

There are many difficulties in this verse; but the simple meaning of the place may be easily apprehended. Noah believed in God; walked uprightly before him, and found grace in his sight; he obeyed him in building the ark, and God made it the means of his salvation from the waters of the deluge. Baptism implies a consecration and dedication of the soul and body to God, the Father, Son, and Holy Spirit. He who is faithful to his baptismal covenant, taking God through Christ, by the eternal Spirit, for his portion, is saved here from his sins; and through the resurrection of Christ from the dead, has the well-grounded hope of eternal glory. This is all plain; but was it the deluge, itself, or the ark, or the being saved by that ark from the deluge, that was the antitype of which St. Peter speaks? Noah and his family were saved by water; i.e. it was the instrument of their being saved through the good providence of God. So the water of baptism, typifying the regenerating influence of the Holy Spirit, is the means of salvation to all those who receive this Holy Spirit in its quickening, cleansing efficacy. Now as the waters of the flood could not have saved Noah and his family, had they not made use of the ark; so the water of baptism saves no man, but as it is the means of his getting his heart purified by the Holy Spirit, and typifying to him that purification. The ark was not immersed in the water; had it been so they must all have perished; but it was borne up on the water, and sprinkled with the rain that fell from heaven. This text, as far as I can see, says nothing in behalf of immersion in baptism; but is rather, from the circumstance mentioned above, in favor of sprinkling. In either case, it is not the sprinkling, washing, or cleansing the body, that can be of any avail to the salvation of the soul, but the answer of a good conscience towards God - the internal evidence and external proof that the soul is purified in the laver of regeneration, and the person enabled to walk in newness of life. We are therefore strongly cautioned here, not to rest in the letter, but to look for the substance.

- Adam Clarke's Commentary on the Bible