سورة At-Tawbah 9:56

وَيَحْلِفُونَ بِٱللَّهِ إِنَّهُمْ لَمِنكُمْ وَمَا هُم مِّنكُمْ وَلَـٰكِنَّهُمْ قَوْمٌۭ يَفْرَقُونَ ٥٦

They swear by Allah that they are part of you, but they are not. They only say so out of fear