Abu Dawud
Purification (Kitab Al-Taharah)
Book Number: 001 / Hadith Number: 193
Narated By 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 (pbuh) 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 (Allahu-Akbar) of the prayer. All this time I was looking at him.