The Old Covenant Passover lamb was sacrificed for a nation. The New Covenant Passover to be radically different. John clarified the difference when he declared:
"Behold! The Lamb of God who takes away the sin of the world," John 1'29.
It was when the time came for Jesus to present Himself to be immersed in water. John "... saw Jesus coming toward him" and he responded.
John's listeners knew about The Passover. However, he was telling them that this "Lamb of God" would totally redefine it.
He was saying the God would pass over every person who looked to the shed blood of this Lamb to "take away" their sins.
Later Jesus Himself said later:
“Most assuredly, I say to you, he who hears My word and believes in Him who sent Me has everlasting life, and shall not come into judgment, but has passed from death into life," John 5'24.
To be found to be "without blemish" the Old Covenant lamb had to be examined. The requirement on Jesus the Lamb of God would be greater.
Towards the end of His three years of being examined He and His Disciples kept the last Old Covenant Feast of Passover differently.
He fulfilled it, transformed it and replaced it. It's "Our Passover", our "Lord's Supper", our "Lord's Table":
"He took bread, gave thanks and broke it, and gave it to them, saying,
'This is My body which is given for you;
do this in remembrance of Me.'
"Likewise He also took the cup after supper, saying,
'This cup is the new covenant in My blood,
which is shed for you'",