In John 6, Jesus states that unless we eat His flesh and drink His blood, we have no life in us.
Jesus said to them, “I tell you the truth, unless you eat the flesh of the Son of Man and drink his blood, you have no life in you. Whoever eats my flesh and drinks my blood has eternal life, and I will raise him up at the last day. For my flesh is real food and my blood is real drink. Whoever eats my flesh and drinks my blood remains in me, and I in him. Just as the living Father sent me and I live because of the Father, so the one who feeds on me will live because of me. This is the bread that came down from heaven. Your forefathers ate manna and died, but he who feeds on this bread will live forever. John 6:53-58 NIV
Could this have been a reference to the Passover Lamb of which the Israelites were supposed to eat all of it? What is the common Protestant understanding of this? Do some traditions associate this with Communion?