Sahih Muslim Book 4, Hadith Number 1247.

Chapter : Excellence of Dhikr after prayer and its description.

Anas reported: A man came panting and entered the row of worshippers and said: Praise be to Allah, much praised and blessed. When the Messenger of Allah (may peace be upon him) finished the prayer he said: Who amongst you uttered these words? The people remained silent. He (the Holy Prophet again said)-: Who amongst you uttered these words? He said nothing wrong. Then a man said: I came and had a difficulty in breathing, so I uttered them. He replied: I saw twelve angels facing one another as to who will take them up (to Allah).