Hadith 4846
وَعَن عمار قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «مَنْ كَانَ ذَا وَجْهَيْنِ فِي الدُّنْيَا كَانَ لَهُ يَوْمَ الْقِيَامَةِ لِسَانَانِ مِنْ نَارٍ» . رَوَاهُ الدَّارمِيّ
Ammar (may Allah be pleased with him) narrates: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever is two-faced in this world, on the Day of Resurrection his tongue will be of fire." Hasan, narrated by al-Darimi.