From Paul Viggiano’s sermon Why In the World Would We Baptize an Infant?
Baptism is not primarily a personal testimony of having saving faith for oneself as much as it is (as we learned earlier) a testimony that God justifies, or saves sinners, by faith. To baptize someone is a rite that points to the truth that righteousness comes by faith. It points to the fact that salvation is based on God’s grace and that we can do nothing to merit it. Baptism points to that truth! It does not necessarily point to the salvation of the person baptized. Baptism is not primarily designed to be a personal testimony of personal saving faith. God commanded circumcision be applied to those whom He knew full well would not be children of faith (e.g., Ishmael, Genesis 17:23).
Does this mean the circumcision was wrongly applied to Ishmael or that it meant nothing? No! It was a sign of man’s only hope. It was a testimony to the saving work of God. Many people are baptized who aren’t saved (see Hebrews 6 and Acts 8). Simon Magus was baptized in Acts 8:13, then in verse 20 Peter says to him, “May your silver perish with you, because you thought you could obtain the gift of God with money!”
Baptism is not a testimony of an individual’s saving faith. It is a testimony that God saves by faith. It is not my personal expression to God. It is God’s expression to me. It is valid and its message is true regardless of the worthiness of the recipient. Baptism is not so much a sign my personal faith as it is a sign and a seal of a covenant promise that God has made to a people—to His people. It’s a beautiful sign when given to an infant because it portrays the spiritual impotence of man and the grace of God toward His powerless creatures. [Emphasis added]
The whole idea that we would only baptize true believers is a flawed concept at best. B.B. Warfield stated the obvious when he asserted that it would be impossible to only baptize true believers because only God knows who the true believers are. He goes on to explain that if we are to baptize based upon our best guess, we should only baptize the children of believers because there is greater likelihood that the children of believers will continue to walk in faith than those who are seemingly converted as adults at crusades and such.
We often hear Baptist (those who oppose infant baptism) parents, who wish to have their children baptized, offer explanations of their children’s salvation based on outward observations. Maybe they said a prayer or made a cohesive statement about the nature of salvation by grace. These are precious and probable causes for the parents to believe their children are following in their spiritual footsteps. The parents still, nonetheless, are making an assumption. If we are going to make assumptions, should they not be Biblical ones?