Have the Torah and Gospel Been Changed?
Question

What sura in the Quran is related or mentions about the corruption of the Torah and Gospel?
Praise be to Allah.What Does the Quran Say About the Alteration of the Torah?
Allah says about the Jews (interpretation of the meaning): {Do you (faithful believers) covet that they will believe in your religion in spite of the fact that a party of them (Jewish rabbis) used to hear the Word of Allah (the Tawrah), then they used to change it knowingly after they understood it?} [Al-Baqarah 2:75]
Qutadah (may Allah have mercy on him) said:
“The phrase ‘then they used to change it knowingly after they understood it’ refers to the Jews, who used to hear the words of Allah, then they altered it after they had understood what it meant.”
Abu `Aliyah (may Allah have mercy on him) said: “They took what Allah had revealed in their Book describing Muhammad (peace and blessings of Allah be upon him), and changed its meaning.”
Ibn Zayd (may Allah have mercy on him) said: “The phrase ‘[they] used to hear the Word of Allah (the Tawrah), then they used to change it’ refers to the Tawrah which Allah revealed to them; they changed it, making what it permitted forbidden, and what was forbidden allowed, changing the truth to falsehood and falsehood to truth…” (Tafsir Ibn Kathir)
Allah also said (interpretation of the meaning): {Among those who are Jews, there are some who displace words from (their) right places and say: ‘We hear your word (O Muhammad) and disobey,’ and ‘Hear and let you (Muhammad) hear nothing.’ And Ra’ina [in Arabic this means, ‘Be careful, listen to us and we listen to you,’ whereas in Hebrew it means ‘an insult.’] with a twist of their tongues and as a mockery of the religion (Islam). And if only they had said, ‘We hear and obey,’ and ‘Do make us understand,’ it would have been better for them, and more proper, but Allah has cursed them for their disbelief, so they believe not except for a few.} [An-Nisa’ 4:46]
The phrase “[they] displace words from (their) right places” means that they misinterpret them and understand them in a way that Allah did not intend, doing this deliberately and inventing lies against Allah. (Tafsir Ibn Kathir)
Allah says (interpretation of the meaning): {So because of their breach of their covenant, We cursed them, and made their hearts grow hard. They change the words from their (right) places and have abandoned a good part of the Message that was sent to them. And you will not cease to discover deceit in them, except a few of them. But forgive them, and overlook (their misdeeds). Verily, Allah loves Al-Muhsinin (good-doers).} [Al-Ma’idah 5:13]
The phrase “because of their breach of their covenant, We cursed them” refers to the fact that they broke the Covenant which had been made with them, so Allah cursed them, i.e., He kept them away from following the True Guidance. “[We] made their hearts grow hard” means that they will not benefit from any preaching because their hearts are so hard. “They change the words from their (right) places” means that they play havoc with the words of Allah and misinterpret His Book, taking it to mean things that were never meant and attributing to Allah things that He never said; may Allah protect us from that.
“[They] have abandoned a good part of the Message that was sent to them” means that they stopped following its teachings because they did not want to follow them.
Al-Hasan (may Allah have mercy on him) said: “They did not adhere to their religion or keep their duties towards Allah, without which no deeds are acceptable to Him; their Fitrah (innate nature) was not sound and their deeds were not righteous.” (Tafseer Ibn Kathir)
How Did the Jews Change the Words of Allah?
So it becomes quite clear that the ways in which the Children of Israel tampered with the Tawrah and Injil include the following:

Changing
Omitting
Adding things and attributing to Allah words that He did not say
Misinterpreting the words of Allah.

The Unaltered Preservation of the Quran
When Muhammad (peace and blessings of Allah be upon him) was sent, the original Tawrah and Injil had already been altered and distorted. Allah revealed the Quran to His Prophet Muhammad (peace and blessings of Allah be upon him), and guaranteed that He Himself would preserve it, as He says (interpretation of the meaning): {Verily We: it is We Who have sent down the Dhikr (i.e., the Quran) and surely, We will guard it (from corruption).} [Al-Hijr 15:9]
This distinguishing feature was not found in any Book before the Quran. From the time of Muhammad (peace and blessings of Allah be upon him) until the present (more than fourteen hundred years) the Quran has stayed the same, and not a single letter of it has been changed, as ancient manuscripts and the hearts of generation after generation of people who have memorized the entire text and earned the title of “Hafidh” bear witness.
We ask Allah to guide us to the true and straight path.
And Allah knows best.