Why do we baptize infants before instructing them in the faith, but baptize adults after they are instructed?
Let’s begin with our Lord’s “words of institution” for Baptism: “Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, teaching them to observe all that I have commanded you” (Matt. 28:19-20). From this we see that baptizing and teaching go hand in hand; disciples (Christians) are made by both. In the case of unbaptized adults, we first teach and then baptize. In the case of infants, first we baptize, and then the teaching follows. In both cases, disciples are made by baptizing and teaching.
We have Scriptural examples of adults first hearing the Gospel (teaching) before they were baptized. The Ethiopian eunuch first studied the Scriptures and heard “the good news about Jesus” (Acts 8:35). Then he saw water and desired to be baptized. See Acts 8:26-38. The jailer in Acts 16:25-34 asked what he must do to be saved. Paul and Silas “spoke the word of the Lord to him and to all who were in his house” (Acts 16:32). First, the jailer and his family heard the Gospel (teaching), and then “he was baptized at once, he and his family” (Acts 16:33).
Why, then, do we baptize infants before teaching the faith to them? We baptize infants with the understanding that they will be taught the faith, primarily by their parents, and live in the life of the Church in the years to come. We baptize infants because they are certainly included in the “all nations” of which Jesus spoke (Matt. 28:19). We recall Jesus’ words: “Let the little children come to Me” (Mark 10:14). We also baptize infants based on Peter’s words: “For the promise is for you and for your children….” (Acts 2:39).
Remember, baptizing and teaching go together. The Lord Jesus did not prescribe a particular order. Instead, He uses both orders—baptizing then teaching or teaching then baptizing—to make disciples.