All Christians should definitely take the time to read John Charter 8 starting at the verse 12 until the end of the Chapter. The Apostle John did an outstanding job describing the heated discussion between some Pharisees and Christ. This is a great Chapter to read, to better understand the divine Nature of Christ.

John 8:
23 And he said unto them, Ye are from beneath; I am from above: ye are of this world; I am not of this world.

John 8:
56 Your father Abraham rejoiced to see my day: and he saw it, and was glad.
57 Then said the Jews unto him, Thou art not yet fifty years old, and hast thou seen Abraham?
58 Jesus said unto them, Verily, verily, I say unto you, Before Abraham was, I am.

Apostle John also revealed in John Chapter one that in the beginning "the Word" was with God, and "the Word" was made flesh and lived among men. Make sure to read this Study:

Christ's Mysteries in John's Gospel and Apostle Paul's Epistle
https://www.brighteon.com/35bec925-e73d-4ff3-aa60-65fd0fcf5245

In the Old Testament, it is reported that Abraham after winirg a war gave Tithes to the King of Salem, Melchizedek. The Name Melchizedek means King of Righteousness and Salem means Peace. It is interesting to note in the following passage that Melchizedek was Priest of the Most High God and brought Bread and Wine:

Genesis 14:
18 And Melchizedek king of Salem brought forth bread and wine: and he was the priest of the most high God.
19 And he blessed him, and said, Blessed be Abram of the most high God, possessor of heaven and earth:
20 And blessed be the most high God, which hath delivered thine enemies into thy hand. And he gave him tithes of all.

About Melchizedek, most likely the Holy Spirit gave to the Apostle Paul an amazing Revelation. Paul did not give any reference to where or how he got this information. It does not really matter, based on Paul's Words we can be certain that just like Christ, the Son of God, Melchizedek was not from this World.

Hebrew 7:
For this Melchisedec, king of Salem, priest of the most high God, who met Abraham returning from the slaughter of the kings, and blessed him;
2 To whom also Abraham gave a tenth part of all; first being by interpretation King of righteousness, and after that also King of Salem, which is, King of peace;
3 Without father, without mother, without descent, having neither beginning of days, nor end of life; but made like unto the Son of God; abideth a priest continually.

Paul also wrote in his Epistle to the Hebrews that the Melchizedek Priesthood is superior to the Levi Priesthood and he explained that in Psalm 110, God with an Oath established Jesus Christ, Priest for ever with the Melchizedek Priesthood.

Psalm 110:
1 The Lord said unto my Lord, Sit thou at my right hand, until I make thine enemies thy footstool.
2 The Lord shall send the rod of thy strength out of Zion: rule thou in the midst of thine enemies.
3 Thy people shall be willing in the day of thy power, in the beauties of holiness from the womb of the morning: thou hast the dew of thy youth.
4 The Lord hath sworn, and will not repent, Thou art a priest for ever after the order of Melchizedek.

Hebrews 7:
25 Wherefore he is able also to save them to the uttermost that come unto God by him, seeing he ever liveth to make intercession for them.
26 For such an high priest became us, who is holy, harmless, undefiled, separate from sinners, and made higher than the heavens;
27 Who needeth not daily, as those high priests, to offer up sacrifice, first for his own sins, and then for the people's: for this he did once, when he offered up himself.

You were provided sufficient scriptural references to draw your own Conclusion, whether or not Christ was referring to the Event in Genesis with Abraham and Melchizedek when he stated that Abraham saw his Day and rejoiced.

Make sure to read:
The most marvelous Revelation of Apostle John:
https://www.brighteon.com/63034f28-db31-4279-ada5-6abeeaac8e0f