In the context of this passage, when John the Baptist says, “Behold the Lamb who takes away the sins of the world”; John is speaking of Messiah as our atoning sacrifice.  Passover was not a sacrifice for sin; the sacrifice for sin was Yom Kippur, the Day of Atonement.  As our High Priest, after His crucifixion, Yeshua presented His own blood in the Tabernacle, not made with hands, and thereby atoned for the sins of the world.    Unlike the earthly Levitical High Priest, who atoned for the sins of Israel year after year, Messiah did it once and for all.  Our High Priest has atoned for the sins of the world whether the world recognizes their sins have been atoned for or not.  Therefore, we can declare with all boldness and confidence that our sins have been atoned for.  We are to live like people whose sins have been forgiven.  When Messiah returns, He is coming for those who recognize what He has done and are looking to His coming.