Selections from The Sayings and Preaching of Amir al-Muminin Ali ibn Abi Talib (Peace Be Upon Him) Including His Replies to Questions and Maxims Expressed for Various Purposes.Translated by Sayyid Ali Reza
وَقَالَ (عليه السلام):
Amir al-mu'minin, peace be upon him, said:
مَا اخْتَلَفَتْ دَعْوَتَانِ
If there are two different calls
إِلاَّ كَانَتْ إِحْدَاهُمَا ضَلاَلَةً.
then one (of them) must be towards misguidance.