John like Jesus was also born under unusual circumstances. His mother Ann was well past her time of being able to conceive. Ann's husband was visited by angels and told that his wife would conceive, when he did not believe he was stuck dumb(unable to speak). John's birth resembles the story of Abraham and Sarah giving birth to Isaac. Sarah was also well past the time of being able to conceive. Angels also visited Abraham to announce the birth of Isaac.

The similarities are stressed to know that what occurred was truly G-d's Will.

John was the last prophet of the Old Testament, Jesus was the first of the New Testament. It is only proper that the last should baptize the first.

Jesus (the Word of God) was the beginning (the New Testament) and the last (the fulfillment of the Old Testament).