عَنْ أَبِي نَمْلَةَ الْأَنْصَارِيِّ رَضِيَ اللَّهُ عَنْهُ قَالَ قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ إِذَا حَدَّثَكُمْ أَهْلُ الْكِتَابِ فَلَا تُصَدِّقُوهُمْ وَلَا تُكَذِّبُوهُمْ وَقُولُوا آمَنَّا بِاللَّهِ وَكُتُبِهِ وَرُسُلِهِ فَإِنْ كَانَ حَقًّا لَمْ تُكَذِّبُوهُمْ وَإِنْ كَانَ بَاطِلًا لَمْ تُصَدِّقُوهُمْ
It is narrated from Sayyiduna Abu Namla Ansari (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: When the People of the Book relate something to you, neither affirm it nor deny it, but say: We believe in Allah, His Books, and His Messengers. Thus, if what they say is true, you have not denied it, and if it is false, you have not affirmed it.