Albert Barnes Commentary John 19:36

"For these things came to pass, that the scripture might be fulfilled, A bone of him shall not be broken." — John 19:36 (ASV)

That the scripture should be fulfilled. See Exodus 12:46. John here regards the paschal lamb as an emblem of Christ; and as in the law it was commanded that a bone of that lamb should not be broken, so, in the providence of God, it was ordered that a bone of the Saviour should not be broken. The Scripture thus received a complete fulfillment respecting both the type and the antitype. Some have supposed, however, that John referred to Psalm 34:20.