General Behavior (Kitab Al-Adab)
Dawud :: Book 41 : Hadith 4829
Narrated Qaylah daughter of Makhramah:
She saw the Prophet (peace_be_upon_him) sitting with his arms round his legs. She said: When I saw the Apostle of Allah (peace_be_upon_him) in such humble condition in the sitting position (according to Musa's version), I trembled with fear.