Tahrif

 (تحريف, ) is a term used in Islam to refer to believed alterations made to the previous revelations of God—specifically those that make up the Torah in Islam or Tawrat, the Zabur or Psalms, and the Gospel in Islam or Injil. The term is also used to refer to what Muslims consider to be the corrupted Jewish and Christian interpretations of the previous revelations of God, known as “Tahrif al-Mana”. This concept holds that earlier revelations have been misinterpreted rather than textually altered.

Origin
The origins of Tahrif are debated. In the 8th century, Muqatil ibn Sulayman claimed in his tafsir on al-Baqara 2:79 of the Quran that the Jews had distorted the Tawrat and removed mention of Muhammad in the Quran in his Tafsir, 2:79. Some academics doubt this as a true mention of tahrif. The 9th century Zaydi scholar al-Qasim al-Rassi claimed that the Jews and Christians had misinterpreted the interpretations of the Tawrat, Zabur, and the Injil. This concept is referred to as tahrif al-mana.

According to Camilla Adang, the early quranic exegete al-Tabari believed that there was a genuine Tawrat of Moses that had been lost and then restored by Ezra alongside a different Torah created by the rabbis and ignorant Jews. Tabari suspected that the Jews of his time were using this different Tawrat instead of the authentic Mosaic one, which is why Tabari made the distinction of referring to the Torah of his time as "The Torah that they possess today" Tabari says elsewhere in his Tafsir of Quran al-Baqara 2:42 that the Jews had introduced falsehood with their own hands in the Torah.

It is worthy to note that some companions of the Prophet such as Uthman (according to Tafsir Ibn Kathir 2:79) and ibn Abbas made some statements that imply he believed the scriptures of ‘the people of the book’ were distorted. In Sahih al-Bukhari, he is quoted saying as narrated by Ubaydallah: "Ibn ʿAbbas said, 'Why do you ask the people of the scripture about anything while your Book (Qur'an) which has been revealed to Allah's Messenger (ﷺ) is newer and the latest? You read it pure, undistorted and unchanged, and Allah has told you that the people of the scripture (Jews and Christians) changed their scripture and distorted it, and wrote the scripture with their own hands and said, 'It is from Allah,' to sell it for a little gain. Does not the knowledge which has come to you prevent you from asking them about anything? No, by Allah, we have never seen any man from them asking you regarding what has been revealed to you!" The corruption of the Biblical text was elaborated more extensively by ibn Hazm in the 11th century, who popularized the concept of tahrif al-nass "corruption of the text". Ibn Hazm rejected claims of Mosaic authorship and posited that Ezra was the author of the Torah. He systematically organised the arguments against the authenticity of the Biblical text in the Hebrew Bible and the New Testament of his book: chronological and geographical inaccuracies and contradictions, theological impossibilities (anthropomorphic expressions, stories of fornication and whoredom, and the attributing of sins to prophets), as well as lack of reliable transmission (tawatur) of the text.

Ibn Hazm explains how the falsification of the Torah could have taken place while only one copy of the Torah existed, kept by the Aaronic priesthood of the Temple in Jerusalem. Ibn Hazm's arguments had a major impact on Muslim literature and scholars, and the themes that he raised concerning tahrif and other polemical ideas were modified slightly by some later authors. The Twelver Shia scholar ibn Babawayh narrated a debate between Ali al-Rida and the catholicos where Ali al-Rida, the 8th Imam of the Twelvers, claimed that the existing Gospels were created and changed after the original Gospel was lost.

Tahrif has also been advocated by Quranist Muslims such as Rashad Khalifa, who believed that previous revelations of God, such as the Bible, contained contradictions due to human interference.

Types
Amin Ahsan Islahi writes about four types of tahrif:
 * 1) To deliberately interpret something in a manner that is opposite to the author's intention. To distort the pronunciation of a word to such an extent that the word changes completely.
 * 2) To add to or delete a sentence or discourse in a manner that distorts the original meaning. For example, according to Muslim tradition, the Jews altered the incident of the migration of Abraham so that no one could prove that Abraham had any relationship with the Kaaba.
 * 3) To translate a word that has two meanings in the meaning that is against the context. For example, the Aramaic word used for Jesus that is equivalent to the ابن  was translated as "son" whereas it also meant "servant" and "slave".
 * 4) To raise questions about something clear to create uncertainty or change it completely.