“Who forsake their beds to cry unto their Lord in fear and hope, and spend of that We have bestowed on them. No soul knoweth what is kept hid for them of joy, as a reward for what they used to do”. (quran, verse)
Then he said: ” Shall I not tell you of the peak of the matter, its pillar, and its topmost part?” I said: “Yes, O Messenger of Allah.” He said: “The peak of the matter is Islam; the pillar is prayer; and its topmost part is jihad.” Then he said: “Shall I not tell you of the controling of all that ?” I said:”Yes, O Messenger of Allah”, and he took hold of his tongue and said: “Restrain this.” I said: “O Prophet of Allah, will what we say be held against us ?” He said: “May your mother be bereaved of you, Muadh ! Is there anything that topples people on their faces – or he said on their noses into Hell-fire other than the jests of their tongues ?”
Related by Al-Tirmithi, who said it was a fine and true hadlth.