A common misunderstanding about baptism is thinking it’s a big sign pointing towards the amount of faith in the one being baptized. But since we can’t read men’s hearts, we’ll never know what degree of faith is present when someone is baptized.
This apparent problem has led some to ask what we should do if someone is baptized but doesn’t mean it, or, from another angle, if a child is baptized in infancy can they really mean it? The reply of Scripture is that regardless of whether the one baptized means it or not, God does (Gal. 3:27, 2 Cor. 5:17, Rom. 6:3, 11). When we’re baptized, God reckons us as His own, He promises all the blessings of union with Christ, and He warns against unbelief.
Baptism isn’t an opportunity to showboat how great our faith is. It’s a sign of how great God’s promise is. A baptized person may not be old enough to grasp it yet, they may go through a season of doubting that promise, or old age may cause the mental recall of their baptism to fade. But God does not forget His promise. In short, when we baptize someone, we aren’t highlighting whether they mean it or not. We’re proclaiming that God means it. We’re simply commanded to trust Him when He says He means it (Mk. 16:16).