Sayyiduna Anas (may Allah be pleased with him) narrates that the Prophet Muhammad (peace be upon him) used to perform nine rak‘ahs of Witr. Then, when the Prophet (peace be upon him) became older and his blessed body became heavier, he started performing seven rak‘ahs of Witr. And the Prophet (peace be upon him) would perform two rak‘ahs sitting, in which he would recite Surah ar-Rahman and Surah al-Waqi‘ah. Sayyiduna Anas (may Allah be pleased with him) says: And we would recite short surahs such as «‏‏‏‏إِذَا زُلْزِلَتِ الْأَرْضُ زِلْزَالَهَا» ‏‏‏‏ and «‏‏‏‏قُلْ يَا أَيُّهَا الْكَافِرُونَ» ‏‏‏‏ and surahs like them.