The familiar phrase “behold the Lamb of God”, which is uttered by St. John the Baptist in today’s Gospel and is said by the priest at every Mass, has a long and rich backstory. It is mentioned in Mass because of the Sacrifice of Christ which is made present at the Mass – a sacrifice foreshadowed by the willingness of Abraham to offer his only son Isaac. When Abraham and Isaac proceed up Mount Moriah (the future Temple Mount in Jerusalem), Isaac asked where the victim of the sacrifice is, to which his father responds “God Himself will provide the lamb for the sacrifice.” A millennium later, the moment finally arrives: John the Baptist, the great prophet who was to precede the Messiah, announces that the promise has finally been fulfilled and God has finally provided the Lamb for the perfect Sacrifice, so he announces: “Behold! The Lamb of God!”
Never forget that this promise is fulfilled at every Mass, and never cease to thank God for the gift of His Son which takes away our sins!