Al-An'am 6:156

An taqooloo innama onzila alkitabuAAala ta-ifatayni min qablina wa-in kunnaAAan dirasatihim laghafileen

[We revealed it] lest you say, "The Scripture was only sent down to two groups before us, but we were of their study unaware,"

(Had We not sent this book,) you would (have an excuse to) say, “The Book was sent down only upon two groups before us, (i.e. the Jews and the Christians) and we were unaware of what they read.”