Hello,
@FlyingDove. Yes, this is very important teaching from our Lord. You can see from verses below how important this teaching is, and just how difficult this teaching is for many people to accept, that it is quite offensive to many then, and is still today.
Read John ch. 6.
https://www.biblegateway.com/passage/?search=John 6&version=NRSV
I am the bread of life. Your ancestors ate the manna in the wilderness, and they died. This is the bread that comes down from heaven, so that one may eat of it and not die. I am the living bread that came down from heaven. Whoever eats of this bread will live forever; and the bread that I will give for the life of the world is my flesh.”
The Jews then disputed among themselves, saying, “How can this man give us his flesh to eat?” So Jesus said to them, “Very truly, I tell you, unless you eat the flesh of the Son of Man and drink his blood, you have no life in you. Those who eat my flesh and drink my blood have eternal life, and I will raise them up on the last day; for my flesh is true food and my blood is true drink. Those who eat my flesh and drink my blood abide in me, and I in them. Just as the living Father sent me, and I live because of the Father, so whoever eats me will live because of me. This is the bread that came down from heaven, not like that which your ancestors ate, and they died. But the one who eats this bread will live forever.” He said these things while he was teaching in the synagogue at Capernaum.
When many of his disciples heard it, they said, “This teaching is difficult; who can accept it?” But Jesus, being aware that his disciples were complaining about it, said to them, “Does this offend you? Then what if you were to see the Son of Man ascending to where he was before? It is the spirit that gives life; the flesh is useless. The words that I have spoken to you are spirit and life. But among you there are some who do not believe.” For Jesus knew from the first who were the ones that did not believe, and who was the one that would betray him. And he said, “For this reason I have told you that no one can come to me unless it is granted by the Father.”
Because of this many of his disciples turned back and no longer went about with him. So Jesus asked the twelve, “Do you also wish to go away?” Simon Peter answered him, “Lord, to whom can we go? You have the words of eternal life. We have come to believe and know that you are the Holy One of God.” Jesus answered them, “Did I not choose you, the twelve? Yet one of you is a devil.” He was speaking of Judas son of Simon Iscariot, for he, though one of the twelve, was going to betray him.
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Also, read these words from the Church fathers for perspective, gives valuable insight > >
http://www.therealpresence.org/eucharst/father/fathers.htm
Also see my sig.
I'm happy to answer questions.
God bless you.