The Qur’an states that the Bible is from Allah (Surah 4:136; 29:46). It even states that the Bible should be examined to test the truthfulness of the Qur’an (10:94).
The problem for Islam is that, in many cases, the Bible (which includes the gospels) contradicts the teachings of the Qur’an. So how do Muslims get around this problem (at least in respect to the gospels)? One way of doing this is to claim that the “Gospel of Barnabas” is actually the correct gospel about Jesus (i.e. the “Injil”) and not the canonical gospels found in the Bible. (Muslims make this claim because the “Gospel of Barnabas” supports some of the Qur’an’s claims.) This, however, does not solve the problem for Muslims because of at least two main issues. First, virtually all scholars (i.e. other than a few Muslim scholars) regard this “gospel” as a forgery of the late Middle Ages. Secondly, this supposed “gospel” actually contradicts the Qur’an on at least one issue. Norman L. Geisler (Ph.D., Loyola University) and Abdul Saleeb (former Muslim) point out that,
…no Muslim should accept the authenticity of The Gospel of Barnabas since it clearly contradicts the Qur’an’s claim that Jesus was the Messiah. It claims, “Jesus confessed, and said the truth; ‘I am not the Messiah… I am indeed sent to the house of Israel as a prophet of salvation; but after me shall come the Messiah” (sects. 42, 48). This is flatly contradictory to the Qur’an, which repeatedly calls Jesus the “Messiah” [the “Christ”] (cf. 5:19, 75).