أَن تَقُولُوٓا۟ إِنَّمَآ أُنزِلَ ٱلْكِتَـٰبُ عَلَىٰ طَآئِفَتَيْنِ مِن قَبْلِنَا وَإِن كُنَّا عَن دِرَاسَتِهِمْ لَغَـٰفِلِينَ
An taqooloo innammaaa unzilal Kitaabu 'alaa taaa'ifataini min qablinaa wa in kunnaa 'an diraasatihim laghaafileen
(اور اس لیے اتاری ہے) کہ (تم یوں نہ) کہو کہ ہم سے پہلے دو ہی گروہوں پر کتابیں اتری تھیں اور ہم ان کے پڑھنے سے (معذور اور) بےخبر تھے
lest you say, "The Book was sent down only to two communities before us, and we were unaware of what they studied,"
The line is a subordinate clause hanging off the instruction given just above it, so 155 through 157 form a single sentence and this is the reason offered for it. Two excuses are shut in turn: here, that scripture went to others and their study was foreign to us; then, that we would have done better had it come to us. Ṭāʾifatayn is a dual left unnamed, which readers filled in as the Jews and Christians.