Parts of the bible in the OT pertain to Israel.
they are also written formoir learning and admonishment
“Moreover, brethren, I would not that ye should be ignorant, how that all our fathers were under the cloud, and all passed through the sea; and were all baptized unto Moses in the cloud and in the sea; and did all eat the same spiritual meat; and did all drink the same spiritual drink: for they drank of that spiritual Rock that followed them: and that Rock was Christ.
But with many of them God was not well pleased: for they were overthrown in the wilderness.
Now these things were our examples, to the intent we should not lust after evil things, as they also lusted. Neither be ye idolaters, as were some of them; as it is written, The people sat down to eat and drink, and rose up to play. Neither let us commit fornication, as some of them committed, and fell in one day three and twenty thousand. Neither let us tempt Christ, as some of them also tempted, and were destroyed of serpents. Neither murmur ye, as some of them also murmured, and were destroyed of the destroyer.
Now
all these things happened unto them for ensamples: and they are written for our admonition, upon whom the ends of the world are come.”
1 Corinthians 10:1-11
while the ot wasn’t originally given to gentiles , it’s intent was the admonishment of the church who would be called later
even the creation story is so we can understand the principle and relationship between faith and Gods word
“Now faith is the substance of things hoped for, the evidence of things not seen.
Through faith we understand that the worlds were framed by the word of God, so that things which are seen were not made of things which do appear.”
Hebrews 11:1, 3 KJV
it also hearkens us to the witness of Christ and the gospel
“In the beginning
God created the heaven and the earth.
And
God said, Let there be light: and there was light.”
Genesis 1:1, 3
“
In the beginning was the Word, and the Word was with God, and the Word was God. The same was in the beginning with God.
All things were
made by him; and without him was not any thing made that was made.
In him was life; and the life was the light of men. And the light shineth in darkness; and the darkness comprehended it not.
That was the true Light, which lighteth every man that cometh into the world. He was in the world, and
the world was made by him, and the world knew him not.”
John 1:1-5, 9-10 KJV