Hadith.1385 - Ays ibn al-Qasim reported from Imam Jafar ibn Muhammad Al-Sadiq (as) who said
"If a man is overcome by sleep while he is in prayer, let him put his head down and sleep, for I fear that if he wishes to say, 'O’ Allah (swt), admit me to Paradise,' he might instead say, 'O’ Allah (swt), admit me to the Fire.'"