Sura al-Baqara 2:76

وَإِذَا لَقُوا۟ ٱلَّذِينَ ءَامَنُوا۟ قَالُوٓا۟ ءَامَنَّا وَإِذَا خَلَا بَعْضُهُمْ إِلَىٰ بَعْضٍ قَالُوٓا۟ أَتُحَدِّثُونَهُم بِمَا فَتَحَ ٱللَّـهُ عَلَيْكُمْ لِيُحَآجُّوكُم بِهِۦ عِندَ رَبِّكُمْ أَفَلَا تَعْقِلُونَ

wa-idhā laqū lladhīna āmanū qālū āmannā wa-idhā khalā baʿḍuhum ilā baʿḍin qālū atuḥaddithūnahum bi-mā fataḥa allāhu ʿalaykum li-yuḥājjūkum bihi ʿinda rabbikum a-fa-lā taʿqilūna

Behold! when they meet the men of Faith, they say: "We believe": But when they meet each other in private, they say: "Shall you tell them what Allah hath revealed to you, that they may engage you in argument about it before your Lord?"- Do ye not understand (their aim)?