Albert Barnes on John 19:36

That the scripture should be fulfilled. See Ex 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 Ps 34:20.