Did the Prophet (peace be upon him) pray eleven rak'ahs every night, or did he sometimes pray fewer than that? And did he pray all of them in the last third of the night, or is it reported that he prayed some of them before sleeping? And how did he pray them?

The Prophet (peace be upon him) used to pray eleven rak'ahs, and sometimes seven, or nine, or thirteen rak'ahs. The time of his standing for prayer varied; he would pray at the beginning of the night, or its middle, or its end. It has been reported that he prayed two light rak'ahs, then two long rak'ahs, then he prayed two rak'ahs that were shorter than the preceding ones, then he prayed two rak'ahs that were shorter than the preceding ones, then two rak'ahs that were shorter than the preceding ones, then he performed Witr. He would pray two rak'ahs at a time (in pairs) and conclude with one rak'ah for Witr.