Exodus 12:21

Draw out and take—and kill the passover.— The word משׁכו mishecu signifies, properly, as we have rendered it, to draw out or take from a number; as if it was said, choose out now, and take you a lamb. It deserves particularly to be remembered, that Moses here calls the paschal lamb by the name of the passover. Kill the passover; i.e. the paschal lamb: a mode of speaking very frequent, both in the Old and New Testament: a little attention to which would have prevented many strange opinions and disputes. Thus Christ calls the bread and wine his body and blood, Mark 14:22; Mark 14:24. Thus St. Paul calls Christ our Passover, 1 Corinthians 5:7. So circumcision is called the covenant, Genesis 17:13.