Purification (Kitab Al-Taharah)
Dawud :: Book 1 : Hadith 193
Narrated Abdullah ibn Harith ibn Jaz':
One of the Companions of the Prophet (may peace be upon), came upon us in Egypt. When he was narrating traditions in the Mosque of Egypt, I heard him say: I was the seventh or the sixth person in the company of the Messenger of Allah ( peace be upon him) in the house of a person.
In the meantime Bilal came and called him for prayer. He came out and passed by a person who had his fire-pan on the fire. The Messenger of Allah (peace_be_upon_him) said to him: Has the food in the fire-pan been cooked? He replied: Yes, my parents be sacrificed upon you. He then took a piece out of it and continued to chew it until he uttered the first takbir (AllahuAkbar) of the prayer. All this time I was looking at him.