We need Spiritual food to Spiritually (eternally) survie:
John (Yahanan):6:3: And Yahshua went up into a mountain, and there He sat with His disciples.
John:6:4: And the Passover, a feast of the Jews, was nigh.
Do you notice in verse 4 what season it is Yahshua claims He is the bread of heaven? That's right, the Passover/Feast of Unleavened Bread season!
Joh:6:25: And when they had found Him on the other side of the sea, they said unto Him, Rabbi, when camest Thou hither?
John:6:26: Yahshua answered them and said, Verily, verily, I say unto you, Ye seek Me, not because ye saw the miracles, but because ye did eat of the loaves, and were filled.
John:6:27: Labour not for the meat which perisheth, but for that meat which endureth unto everlasting life, which the Son of man shall give unto you: for Him hath YaHVeH the FATHER sealed.
John:6:28: Then said they unto Him, What shall we do, that we might work the works of Elohim?
John:6:29: Yahshua answered and said unto them, This is the work of YaHVeH, that ye believe on Him whom HE hath sent.
John:6:30: They said therefore unto Him, What sign shewest Thou then, that we may see, and believe Thee? what dost Thou work?
John:6:31: Our fathers did eat manna in the desert; as it is written, he gave them bread from heaven to eat.
The people were implying that Moses gave the bread, Yahshua corrects them in their misunderstanding:
John:6:32: Then Yahshua said unto them, Verily, verily, I say unto you, Moses gave you not that bread from heaven; but My FATHER giveth you the true bread from heaven.
John:6:33: For the bread of YaHVeH is He which cometh down from heaven, and giveth life unto the world.
John:6:34: Then said they unto Him, Adonai, evermore give us this bread.
John:6:35: And Yahshua said unto them, I am the bread of life: he that cometh to Me shall never hunger; and he that believeth on me shall never thirst.
Did you catch that? Yahshua clearly and plainly said He is "the bread of life" (Mat. 5:17; Galatian 3:24; Luke 24:44). He is the manna from heaven and He is the unleavened bread eaten during the Feast of Unleavened Bread, and it is our faith Him that will sustain us for all eternity!
John:6:36: But I said unto you, That ye also have seen Me, and believe not.
John:6:37: All that the FATHER giveth Me shall come to Me; and him that cometh to Me I will in no wise cast out.
John:6:38: For I came down from heaven, not to do Mine own will, but the will of HIM that sent Me.
John:6:39: And this is the FATHER's will which hath sent Me, that of all which HE hath given Me I should lose nothing, but should raise it up again at the last day.
John:6:40: And this is the will of HIM that sent Me, that every one which seeth the Son, and believeth on Him, may have everlasting life: and I will raise him up at the last day.
John:6:41: The Jews then murmured at Him, because He said, I am the bread which came down from heaven.
John:6:42: And they said, Is not this Yahshua, the son of Joseph, whose father and mother we know? how is it then that He saith, I came down from heaven?
John:6:43: Yahshua therefore answered and said unto them, Murmur not among yourselves.
John:6:44: No man can come to me, except the FATHER which hath sent Me draw him: and I will raise him up at the last day.
John:6:45: It is written in the prophets, And they shall be all taught of YaHVeH. Every man therefore that hath heard, and hath learned of the FATHER, cometh unto Me.
John:6:46: Not that any man hath seen the FATHER, save He which is of Elohim, He hath seen the FATHER.
John:6:47: Verily, verily, I say unto you, he that believeth on Me hath everlasting life.
John:6:48: I am that bread of life.
John:6:49: Your fathers did eat manna in the wilderness, and are dead.
John:6:50: This is the bread which cometh down from heaven, that a man may eat thereof, and not die.
John:6:51: I am the living bread which came down from heaven: if any man eat of this bread, he shall live for ever: and the bread that I will give is my flesh, which I will give for the life of the world.
Notice Yahshua did not say He was giving His life just for the children of Israel, He said "the life of the WORLD!"
John:6:52: The Jews therefore strove among themselves, saying, How can this Man give us His flesh to eat?
John:6:53: Then Yahshua said unto them, Verily, verily, I say unto you, Except ye eat the flesh of the Son of Man, and drink His blood, ye have no life in you.
John:6:54: Whoso eateth My flesh, and drinketh My blood, hath eternal life; and I will raise him up at the last day.
John:6:55: For My flesh is meat indeed, and My blood is drink indeed.
John:6:56: He that eateth My flesh, and drinketh My blood, dwelleth in Me, and I in him.
John:6:57: As the living FATHER hath sent Me, and I live by the FATHER: so he that eateth Me, even he shall live by Me.
John:6:58: This is that bread which came down from heaven: not as your fathers did eat manna, and are dead: he that eateth of this bread shall live for ever.
John:6:59: These things said he in the synagogue, as he taught in Capernaum.
John:6:60: Many therefore of His disciples, when they had heard this, said, This is an hard saying; who can hear it?
John:6:61: When Yahshua knew in Himself that His disciples murmured at it, He said unto them, Doth this offend you?
John:6:62: What and if ye shall see the Son of Man ascend up where He was before?
John:6:63: It is the spirit that quickeneth; the flesh profiteth nothing: the words that I speak unto you, they are spirit, and they are life.
John:6:64: But there are some of you that believe not. For Yahshua knew from the beginning who they were that believed not, and who should betray Him.
John:6:65: And He said, Therefore said I unto you, that no man can come unto Me, except it were given unto him of My FATHER.
John:6:66: From that time many of His disciples went back, and walked no more with Him.
John:6:67: Then said Yahshua unto the twelve, Will ye also go away?
Joh:6:68: Then Simon Peter answered Him, Adonai, to whom shall we go? thou hast the words of eternal life.
John:6:69: And we believe and are sure that thou art that Messiah, the Son of the living Elohim.
Joh:6:70: Yahshua answered them, Have not I chosen you twelve, and one of you is a devil?
John:6:71: He spake of Judas Iscariot the son of Simon: for he it was that should betray Him, being one of the twelve.
I believe John chapter 6 is self explanator. It is our faith in those things that we cannot see that we have our hope in (Hebrews 11:1).