It wasnarrated that Abu Dharr said:
"We fasted Ramadan with theMessengerof Allah (ﷺ) and he did not lead us in praying Qiyam(prayers atnight) during any part of it, until there were sevennights left. Heled us in praying Qiyam on the seventh night untilapproximately onethird of the night had passed. Then on the sixthnight which followedit he did not lead us in prayer. Then he led usin praying Qiyam onthe fifth night which followed it until almosthalf the night hadpassed. I said: 'O Messenger of Allah, would thatwe had offeredvoluntary prayers throughout the whole night.' He said:'Whoeverstands with the Imam until he finishes, it is equivalent tospendingthe whole night in prayer.' Then on the fourth night whichfollowedit, he did not lead us in prayer, until the third night thatfollowedit, when he gathered his wives and family, and the peoplegathered,and he led us in prayer until we feared that we would misstheFalah." It was asked: "What is the Falah?" He said: "Suhur."Hesaid: "Then he did not lead us in prayer at night for the restof themonth."
English reference: Vol. 1, Book 5, Hadith 1327
Arabic reference: Book 5, Hadith 1388