Faith is what you do to fulfill the condition for eternal life or salvation.  Forgiveness is what God does.  And he does that at baptism.  Hence, when Jesus spoke about salvation, he conjoined the two acts: “Whoever believes and is baptized will be saved…”[1]

Opponents of baptism argue that because John 3.16 (and other verses) mentions only faith in connection with salvation (eternal life), then faith alone is necessary for salvation.  However, since Luke 13.3 mentions only repentance in connection with salvation (will not perish), are opponents of baptism preaching that repentance alone is necessary for salvation?  Similarly, John 13.8 mentions only footwashing in connection with salvation (part with Christ), and 1 Peter 3.21 mentions only baptism in connection with salvation.  There are two ways to interpret all these – as contradictory or as complementary.  If they are contradictory, you do one and ignore the rest.  If they are complementary, you do all.  If you believe that the word of God is not contradictory, you do all.

[1] Mk 16.16.