In the Ancient Church a Christian was a person who turned from idols and embraced the living God as he had revealed himself definitively in the crucified and risen Christ (1 Thessalonians 1:9-10). What made him a Christian? Faith, which was rooted in the electing work of God (see Acts 11:18; 13:48; 15:7-9; 16:31). None of the early New Testament authors believed that the act of baptism alone saved anyone (thus Mark 16:16). Baptism is the way a person with a good conscience (to see what this is and how one obtains it, read Hebrews 9:14) responds to the saving work of God. Thus 1 Peter 3:21 means that the baptism which saves is that which is “the pledge of a good conscience toward God.”
These convictions must be asserted afresh today for the upholders of the so-called Federal Vision maintain that the baptism of infants makes them Christians—a position that is simply taking us back to the disastrous confusion of the medieval Church. As a Calvinistic Baptist I have deep admiration for many Reformed paedobaptist brothers, though I would disagree with their argument that infant baptism is a covenantal sign that must be affirmed later in life. But such brethren do not argue for trust for salvation in the baptismal rite. There must be conversion.
But this position is quite different from the affirmation that a human rite in itself and by itself saves. The Apostle clearly rejects this latter argument in 1 Corinthians 10:1-5. If participation in the ordinances saved, then surely those who followed Moses out of Egypt would have entered the Promised Land. But they did not—for baptism (and the Lord’s Table) do not save.
God will not give the glory of being the Saviour of his people to another person or thing!