A Guide to Mankind:-
2: 185 Ramadan is the (month) in which was sent down the Qur'an as a guide to mankind [huda lil nass] also clear (Signs) for guidance and judgment (between right and wrong). So everyone of you who is present (at his home) during that month should spend it in fasting but if anyone is ill or on a journey the prescribed period (should be made up) by days later. Allah intends every facility for you He does not want to put you to difficulties. (He wants you) to complete the prescribed period and to glorify Him in that He has guided you; and perchance ye shall be grateful.
3: 2 Allah! there is no god but He the Living the Self-Subsisting Eternal. 3 It is He Who sent down to thee (step by step) in truth the Book confirming what went before it; and He sent down Law (Of Moses) and the Gospel (of Jesus) 4 before this as a guide to mankind [huda lil nass] and He sent down the Criterion
(of judgment between right and wrong).
*** The Quran declares that Allah did not only send the Book to Moses but also the Gospels to Jesus.
These two Books, together are stated to be also, " a guide to Mankind…" and are obviously not corrupted.
Muhammad and his Quran are of course in manifest error when they assert that Allah sent the Gospels to Jesus since the Gospels were only written long after Jesus was dead and Allah had nothing whatsoever to do with them***