This is day 2 of Jesus’ ministry. John sees Jesus coming towards him and uses the phrase “Lamb of God who takes away the sin of the world” for the first time. This concept would have been earth shattering to a Jew. The concept of an animal absorbing sin in place of man was quite familiar to the Jews. John’s statement now introduces the concept of God being the sacrifice for the sin of the entire world -not just for the Jewish nation. This is utterly unthinkable and incredibly shocking on two accounts: That instead of a lamb for sacrifice, it would be God Himself and That the sacrifice would atone for all of mankind, not just for the Jews. This would have been earth shattering and probably offensive to the Jews.
John would have been quite familiar with the Jewish sacrificial system since he was the son of a priest (Zechariah). Every morning and evening a lamb was sacrificed at the temple for the sins of the people. This was a practice that had to be done repeatedly. John the Baptist confidently looks at Jesus and gives Jesus the title He so rightly deserves, regardless of who might be offended. John points others to Jesus with this proclamation, especially his own disciples.