For example, let's take melchizedek. All it says in the OT is this:
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.
So how did you get all that other stuff about Melchizedek being associated with Jesus Christ from such skimpy material? Jesus Christ or messiah isn't even mentioned in those 3 verses. But here's what Wiki says about Melchizedek:
Association with the Messiah
The association or identification of Melchizedek with the Messiah predates Christianity, developing in Jewish messianism of the Second Temple period.[citation needed]
A collection of early Gnostic scripts dating on or before the 4th century, discovered in 1945 and known as the Nag Hammadi library, contains a tractate pertaining to Melchizedek. Here it is proposed that Melchizedek is Jesus Christ.[70] Melchizedek, as Jesus Christ, lives, preaches, dies and is resurrected, in a gnostic perspective. The Coming of the Son of God Melchizedek speaks of his return to bring peace, supported by God, and he is a priest-king who dispenses justice.[71]
The association with Christ is made explicit by the author of the Epistle to the Hebrews, where Melchizedek the "king of righteousness" and "king of peace" is explicitly associated with the "eternal priesthood" of the Son of God.[72] The Christological interpretation of this Old Testament character being a prefiguration or prototype of the Christ has varied between Christian denominations. The Pelagians saw in Melchizedek merely a man who lived a perfect life.[73]
Typological association of Jesus Christ with Old Testament characters occurs frequently in the New Testament and in later Christian writings; thus, Jesus Christ is also associated with Adam (as the "New Adam") and with Abraham.[74] The bread and wine offered by Abraham to Melchizedek has been interpreted by church fathers including Clement of Alexandria as being a prefiguration of the Eucharist.[75]
As you can see from the bold underline it was the Gnostics who associated Melchizedek with Jesus alothough there had been association in OT times. ---Wikipedia
All this has no basis in scripture. It's just ideas and beliefs based on nothing.
Depends what you mean by scripture. If only the OT, then very little is written -and one has to consider whether there was even any idea of a Messiah put forth at the time of the writing -that he would become Messiah -similar to how it was not revealed initially that God allowing no flesh, then all flesh to be eaten woukd continue with only some -then eventually none again later. God knows what he declared from the beginning, but reveals it over time -declaring it. first through the prophets, etc.
Though I will look for more indications in the OT only when possible, if a psalm indicates that the priesthood of Melchizedek is everlasting.... and people meticulous about genealogy have no recorded lineage to or from him.... the idea that he is not man as such, but not the most high God, is understandable.
(The following associates him with what Messiah is to DO -but does not use the word..... note that THE Lord speaks to one the psalmist calls MY Lord...
The LORD said unto my Lord, Sit thou at my right hand, until I make thine enemies thy footstool.
2The LORD shall send the rod of thy strength out of Zion: rule thou in the midst of thine enemies.
3Thy 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.
4The LORD hath sworn, and will not repent, Thou
art a priest for ever after the order of Melchizedek.
5The Lord at thy right hand shall strike through kings in the day of his wrath.
6He shall judge among the heathen, he shall fill
the places with the dead bodies; he shall wound the heads over many countries)
There would, however, have been ideas, beliefs even at the time of writing which may not have been recorded.
The NT does go into much detail associating Christ with and AS Melchizedek (search ...without beginning of days or end of life -high priest continually -unchanging priesthood, etc.)
