John 1:36

and as he saw Jesus passing by he said, "Look! He is the Lamb of God!"

John 1:29

The next day John saw Jesus coming toward him, and he said, "Look! He is the Lamb of God who is to take away the world's sin.

Hebrews 12:2

keeping our eyes on Jesus, the perfect leader and example of faith, who, instead of the joy which lay before Him, endured the cross with no regard for its shame, and since has taken His seat at the right hand of the throne of God.

1 Peter 1:19-20

but with the precious blood of Christ, like that of a lamb without a blemish or a blot,

Treasury of Scripture Knowledge

Summary

And looking upon Jesus as he walked, he saith, Behold the Lamb of God!

Bible References

Behold

John 1:29
The next day John saw Jesus coming toward him, and he said, "Look! He is the Lamb of God who is to take away the world's sin.
Hebrews 12:2
keeping our eyes on Jesus, the perfect leader and example of faith, who, instead of the joy which lay before Him, endured the cross with no regard for its shame, and since has taken His seat at the right hand of the throne of God.
1 Peter 1:19
but with the precious blood of Christ, like that of a lamb without a blemish or a blot,