Protestant churches that practice infant baptism include most Lutheran, Presbyterian, Methodist, Episcopalian, Anglican and Reformed churches. Protestant Churches that only baptize adults or children who have repented include Baptist, Pentecostal, Nazarene, Charismatic, Wesleyan, Church of God, Assembly of God and Adventist. Similarly, when we see people baptized in the Bible it always followed their repentance or belief.
Most Protestants therefore believe that baptism confirms our decision to repent.
Therefore, if a person has not repented, then their baptism confirms nothing and is invalid. This is what John the Baptist was apparently referring to when a crowd of unrepentant persons came to him seeking baptism, in Matt. To repent, of course, and live for God. Repentance and baptism are always linked in the scripture. In line with this understanding, we find no case in scripture of an infant being baptized, since an infant is unaware of right and wrong and therefore has nothing of which to repent.