Ibn `Abbas said that,

وَالَّذِينَ يُؤْمِنُونَ بِمَآ أُنزِلَ إِلَيْكَ وَمَآ أُنزِلَ مِن قَبْلِكَ

(And who have faith in what is revealed to you and in what was revealed before you.) means, "They believe in what Allah sent you with, and in what the previous Messengers were sent with, they do not distinguish between (believing) them, nor do they reject what they brought from their Lord."

This verse speaks of some other attributes of the God-fearing, giving certain details about faith in the unseen with a special mention of faith in hereafter. Commenting on this verse, the blessed Companions ` Abdullah ibn Masud and ` Abdullah ibn ` Abbs ؓ have said that in the days of the Holy Prophet ﷺ God-fearing Muslims were of two kinds, - those who used to be associators and disbelievers but accepted Islam, and those who used to be among the people of the Book (that is, Jews and Christians) but embraced Islam later on; the preceding verse refers to the first group, and this verse to the second. Hence this verse specifically mentions belief in the earlier Divine Books along with belief in the Holy Qur'an, for, according to the Hadith, people in the second group deserve a double recompense, firstly, for believing in and following the earlier Books before the Holy Qur'an came to replace them, and secondly, for believing in and following the Holy Qur'an when it came as the final Book of Allah. Even today it is obligatory for every Muslim to believe in the earlier Divine Books except that now the belief has to take this form: everything that Allah has revealed in the earlier Books is true (excepting the changes and distortions introduced by selfish people), and that it was incumbent upon the people for whom those Books had been sent to act according to them, but now that all the earlier Books and Shari'ahs have been abrogated, one must act according to the Holy Qur'an alone.3

3\. Exactly as predicted by a Hadith, today we see all around us a proliferation of "knowledge" and of "writing". One of the dangerous forms the process has taken is the indiscriminate translation at least into European languages and the popularization of the sacred books of all possible religious and metaphysical traditions - not only the Hindu, the Chinese or the Japanese, but also the Shamanic or the Red Indian. The lust for reading sacred books has virtually grown into a mania, especially among the modern young people with their deep sense of being uprooted and disinherited, and all considerations of aptitude have been contemptuously set aside. In these circumstances, Muslims with a Western orientation are naturally impelled to ask themselves as to what they can or should make of such books which sometimes seem to offer similarities and parallels to the Holy Qur'an itself, and more often to the Sufi doctrines. The problem has already attained noticeable proportions, for in 1974 the government of Turkey found it necessary to ban the entry of certain Hindu sacred books like the Bhagavadgita and Upanishads. The correct doctrinal position in this respect is that it is obligatory for every Muslim, as an essential part of the Islamic creed, to believe in all the prophets and messengers of Allah and in the Divine Books (not in their distorted forms, but as they were originally revealed) that have specifically been mentioned by their names in the Holy Qur'an, and also to believe that Allah has sent His messengers and His books for the guidance of all the peoples and all the ages, and that Muhammad ﷺ is the last prophet and the Holy Qur'an the final Book of Allah which has come down to replace the earlier Books and Shari'ahs. As to the question of the authenticity and divine origin of a particular book held in reverence by an earlier religion or metaphysical tradition, a Muslim is not allowed to affirm such a claim unequivocally, nor should he unnecessarily reject such a possibility. In so far as contents of the book concerned agree with what the Holy Qur'an has to say on the subject, we may accept the statement as true, otherwise spiritual etiquette requires an average Muslim to keep quiet and not meddle with things which he is not likely to understand. As for reading the sacred books of other traditions, it should be clearly borne in mind that a comparative study of this nature requires a very special aptitude which is extremely rare, and hence demands great caution. A cursory reading of sacred books, motivated by an idle curiosity or by a craze for mere information, may very well lead to an intellectual disintegration or to something still worse, instead of helping in the "discovery of the truth" and the acquisition of "peace" which a comparative study is widely supposed to promise. Even when the aptitude and the knowledge necessary for the task is present, such a study can be carried out only under the supervision of an authentic spiritual master. In any case, we cannot insist too much on the perils of the enterprise.