"The Eucharist" is not mentioned in the Bible as such, and "transubstantiation" is also not a Bible teaching, IMO. Such rituals may soothe some people, but impart nothing that draws one closer to God. (Matthew 15:9)
The word "Eucharist" is not in the Bible but the subject of it is, in my opinion.
When you come together, it is not really to eat the Lord's supper. For when the time comes to eat, each of you goes ahead with your own supper, and one goes hungry and another becomes drunk. What! Do you not have homes to eat and drink in? Or do you show contempt for the church of God and humiliate those who have nothing? What should I say to you? Should I commend you? In this matter I do not commend you! For I received from the Lord what I also handed on to you, that the Lord Jesus on the night when he was betrayed took a loaf of bread, and when he had given thanks, he broke it and said, 'This is my body that is for you. Do this in remembrance of me.' In the same way he took the cup also, after supper, saying, 'This cup is the new covenant in my blood. Do this, as often as you drink it, in remembrance of me.' For as often as you eat this bread and drink the cup, you proclaim the Lord's death until he comes. Whoever, therefore, eats the bread or drinks the cup of the Lord in an unworthy manner will be answerable for the body and blood of the Lord. Examine yourselves, and only then eat of the bread and drink of the cup. For all who eat and drink without discerning the body, eat and drink judgement against themselves. For this reason many of you are weak and ill, and some have died. But if we judged ourselves, we would not be judged. But when we are judged by the Lord, we are disciplined so that we may not be condemned along with the world. So then, my brothers and sisters, when you come together to eat, wait for one another. If you are hungry, eat at home, so that when you come together, it will not be for your condemnation. About the other things I will give instructions when I come.
(1 Corinthians 11:20-34 NRSV-CE)
These are blemishes on your love-feasts, while they feast with you without fear, feeding themselves. They are waterless clouds carried along by the winds; autumn trees without fruit, twice dead, uprooted; wild waves of the sea, casting up the foam of their own shame; wandering stars, for whom the deepest darkness has been reserved for ever.
(Jude 1:12-13 NRSV-CE)
They devoted themselves to the apostles' teaching and fellowship, to the breaking of bread and the prayers.
(Acts 2:42 NRSV-CE)
Do not work for the food that perishes, but for the food that endures for eternal life, which the Son of Man will give you. For it is on him that God the Father has set his seal.' Then they said to him, 'What must we do to perform the works of God?' Jesus answered them, 'This is the work of God, that you believe in him whom he has sent.' So they said to him, 'What sign are you going to give us then, so that we may see it and believe you? What work are you performing? Our ancestors ate the manna in the wilderness; as it is written, "He gave them bread from heaven to eat."' Then Jesus said to them, 'Very truly, I tell you, it was not Moses who gave you the bread from heaven, but it is my Father who gives you the true bread from heaven. For the bread of God is that which comes down from heaven and gives life to the world.' They said to him, 'Sir, give us this bread always.' Jesus said to them, 'I am the bread of life. Whoever comes to me will never be hungry, and whoever believes in me will never be thirsty. But I said to you that you have seen me and yet do not believe. Everything that the Father gives me will come to me, and anyone who comes to me I will never drive away; for I have come down from heaven, not to do my own will, but the will of him who sent me. And this is the will of him who sent me, that I should lose nothing of all that he has given me, but raise it up on the last day. This is indeed the will of my Father, that all who see the Son and believe in him may have eternal life; and I will raise them up on the last day.' Then the Jews began to complain about him because he said, 'I am the bread that came down from heaven.' They were saying, 'Is not this Jesus, the son of Joseph, whose father and mother we know? How can he now say, "I have come down from heaven"?' Jesus answered them, 'Do not complain among yourselves. No one can come to me unless drawn by the Father who sent me; and I will raise that person up on the last day. It is written in the prophets, "And they shall all be taught by God." Everyone who has heard and learned from the Father comes to me. Not that anyone has seen the Father except the one who is from God; he has seen the Father. Very truly, I tell you, whoever believes has eternal life. 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 for ever; 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 for ever.' He said these things while he was teaching in the synagogue at Capernaum.
(John 6:27-59 NRSV-CE)
There are more verses in the Bible that concern it but I won't post them all.
