Please provide evidence from the Bible where God promised to guard it from corruption.
Christians love their Holy Scriptures and would never let anyone change them. The Bible warns that those who try to change God’s Word will be severely punished. A long time ago God spoke through Moses (in the Torah) commanding, “You shall not add to the word which I command you, nor take from it, that you may keep the commandments of the Lord your God which I command you”(Torah, Deuteronomy 4:2).
Two centuries later Solomon said, “Every word of God is pure. He is a shield to those who put their trust in Him. Do not add to His words, lest He rebuke you, and you be found a liar” (Proverbs 30:5-6).
Here is what He says in the Psalms ~ “Forever O Lord, Your Word is settled in Heaven” (Psalm 119:89).
The prophet Isaiah said, “The grass withers, the flower fades,
But the word of our God stands forever.” (Isaiah 40:8)
Jesus said, “Do not think that I came to destroy the Law or the Prophets. I did not come to destroy but to fulfill. For assuredly, I say to you, till heaven and earth pass away, one jot or one tittle will by no means pass from the law till all is fulfilled. ” ( Matthew 5: 18) Later he also said, “Heaven and earth will pass away, but My Words will by no means pass away.” (Matthew 24:35).
Here is what He says in the Psalms ~ “Forever O Lord, Your Word is settled in Heaven” (Psalm 119:89).
Even when the last book of the Bible was written, God said through the apostle John, “I testify to everyone who hears the words of the prophecy of this book: If anyone adds to these things, God will add to him the plagues that are written in this book. And If anyone takes away from the words of the book of this prophecy, God shall take away his part from the book of life, from the holy city, and from the things which are written in this book”(Revelation 22:18-19).
These warnings are clear. No believer would dare to change God’s word.
Sahih International
Indeed, it is We who sent down the Qur'an and indeed, We will be its guardian.
Muhsin Khan
Verily We: It is We Who have sent down the Dhikr (i.e. the Quran) and surely, We will guard it (from corruption).
15:9
So why do you assume that Our God would keep this promise for the Quran yet fail in his promise for the Bible?
If that is the case then the Holy Qur'an corrects it.
Maybe you have a different criteria for measuring a prophet in the Quran.