“What is THIS?”
Paul can answer that, in 1 Corinthians 11:23-30
“23 For I have received of the Lord that which also I delivered unto you, that the Lord Jesus, the same night in which he was betrayed, took bread 24 And giving thanks, broke, and said: Take ye, and eat: this is my body, which shall be delivered for you: this do for the commemoration of me. 25 In like manner also the chalice, after he had supped, saying: This chalice is the New Testament in my blood: this do ye, as often as you shall drink, for the commemoration of me.
26 For as often as you shall eat this bread, and drink the chalice, you shall shew the death of the Lord, until he come. 27 Therefore whosoever shall eat this bread, or drink the chalice of the Lord unworthily, shall be guilty of the body and of the blood of the Lord. 28 But let a man prove himself: and so let him eat of that bread, and drink of the chalice. 29 For he that eateth and drinketh unworthily, eateth and drinketh judgment to himself, not discerning the body of the Lord. 30 Therefore are there many infirm and weak among you, and many sleep.”
Not merely the old covenant, the Passover meal.
Put all that together with the last half of John 6.
None of this is a suggestion. It’s our half of the covenant, the new contract.
See https://freerepublic.com/focus/chat/4141352/posts?page=50#50 and http://peacebyjesus.net/the_lord%27s_supper.html
THIS bread; THIS chalice: Passover meal