It is narrated from Sayyiduna Sa’d bin Abi Waqqas (may Allah be pleased with him) that he used to perform the ‘Isha prayer in the Prophet’s Mosque and would offer one rak‘ah of Witr and not add anything to it. Someone asked him, “O Abu Ishaq! Do you not add anything after offering one rak‘ah of Witr?” He replied, “Yes! I heard the Prophet (peace and blessings be upon him) say: ‘Whoever does not sleep without offering Witr is wise.’”