Mark 1:4 - Matthew Poole's English Annotations on the Holy Bible

Luke saith that John began about the fifteenth year of Tiberius Caesar. He baptized in the wilderness, that is, a place little inhabited. By his baptism is not to be strictly understood baptism, but his preaching and doctrine, his whole administration; which is called the baptism of repentance, because repentance was the great thing he preached, a seal of which baptism was to be; the consequent of which was to be the remission of sins, or the argument which he used to press repentance was the remission of sins. See Poole on "Matthew 3:5". See Poole on "Matthew 3:6", where we before had these words.