John 1:51

He then added, “I tell you the truth, you shall see heaven open, and the angels of God ascending and descending on the Son of Man.”

“heaven open” is the symbol of free intercourse between God and man (Mt 3:16; Lu 3:21; Isa 64:1; Ac 7:56) which was accomplished by Christ (Heb 10:19-22).

Matt 3:16  As soon as Jesus was baptised, he went up out of the water. At that moment heaven was opened, and he saw the Spirit of God descending like a dove and lighting on him.

Luke 3:21  When all the people were being baptised, Jesus was baptised too. And as he was praying, heaven was opened

Isaiah 64:1 Oh, that you would rend the heavens and come down, that the mountains would tremble before you!

Acts 7:56  “Look,” he said, “I see heaven open and the Son of Man standing at the right hand of God.”

Heb 10:19-22  Therefore, brothers, since we have confidence to enter the Most Holy Place by the blood of Jesus, by a new and living way opened for us through the curtain, that is, his body,  and since we have a great priest over the house of God, let us draw near to God with a sincere heart in full assurance of faith, having our hearts sprinkled to cleanse us from a guilty conscience and having our bodies washed with pure water.

“angels . . . ” cf. “And he dreamed, and behold a ladder set up on the earth, and the top of it reached to heaven: and behold the angels of God ascending and descending on it.” (Genesis 28:12 KJV)

Genesis 28:12  He had a dream in which he saw a stairway resting on the earth, with its top reaching to heaven, and the angels of God were ascending and descending on it.

Notice that the ladder is equated by Jesus as being Himself. What is the function of a ladder?  How does Jesus fulfill this function between us and heaven?

“Son of man” (Dan 7:13,14). Note that Jesus is both the Son of God as Nathanael called Him and the Son of man as Jesus called Himself. What does this have to do with Him being the ladder between earth and heaven?

Dan 7:13-14  “In my vision at night I looked, and there before me was one like a son of man, coming with the clouds of heaven. He approached the Ancient of Days and was led into his presence. He was given authority, glory and sovereign power; all peoples, nations and men of every language worshipped him. His dominion is an everlasting dominion that will not pass away, and his kingdom is one that will never be destroyed.