It is narrated from Sayyiduna Sufyan bin Abdullah that I once submitted in the court of the Messenger: O Messenger of Allah! Tell me something about Islam such that after you, I would not need to ask anyone else anything. The Prophet (peace be upon him) said: First, declare with your tongue that I have believed in Allah, then remain steadfast upon it always. I asked: O Messenger of Allah! From what should I guard myself? The Prophet (peace be upon him) pointed towards his tongue.