The Book of Prayers (Kitab Al-Salat)
Muslim :: Book 4 : Hadith 1247
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).