Al-Baqarah 2:76

Wa-itha laqoo allatheena amanooqaloo amanna wa-itha khalabaAAduhum ila baAAdin qaloo atuhaddithoonahumbima fataha Allahu AAalaykum liyuhajjookumbihi AAinda rabbikum afala taAAqiloon

And when they meet those who believe, they say, "We have believed"; but when they are alone with one another, they say, "Do you talk to them about what Allāh has revealed to you so they can argue with you about it before your Lord?" Then will you not reason?

When they meet those who believe, they say, “We believe.” But when some of them meet others in private, they say, “Do you tell them (the Muslims) what Allah has disclosed to you so that they may thereby argue against you before your Lord? Will you, then, not use reason?”