“Some pretend that children, not as yet having 'reason,' ought not to receive  baptism. I answer: That reason in no way contributes to faith...
If God can communicate the Holy Spirit to grown persons, he can communicate it  to young  children. Faith comes of the Word of God, when this is heard; little  children hear that Word when they receive baptism, and therewith they receive  also faith.”
~ Martin Luther, Table Talk