Example in the Quran

وَإِذَا لَقُواْ ٱلَّذِينَ ءَامَنُواْ قَالُوٓاْ ءَامَنَّا وَإِذَا خَلَوۡاْ إِلَىٰ شَيَٰطِينِهِمۡ قَالُوٓاْ إِنَّا مَعَكُمۡ إِنَّمَا نَحۡنُ مُسۡتَهۡزِءُونَ

When they meet the believers they say, “We believe.” But when alone with their evil associates they say, “We are definitely with you; we were only mocking.”