"The companions of Allah's Messenger would sleep, then stand to pray, They would not perform Wudu."
Jami` at-Tirmidhi Book 1, Hadith 78
← Previous Hadith he saw the Prophet sleeping, while in the prostration position, until he snored or snorted. Then he stoodup to pray. So I said: "O Messenger of Allah! You were sleeping?" He said: "Wudu is not required except for sleeping while reclining. For when one reclines, joints relax."

Jami` at-Tirmidhi Book 1, Hadith 77 Next Hadith → Allah's Messenger said: "Wudu is (required) from what fire has touched, even if it be a piece of cheese."

Jami` at-Tirmidhi Book 1, Hadith 79