`Sayyiduna Abdullah bin Abbas (may Allah be pleased with them) says that the prayer of the Noble Prophet (peace and blessings of Allah be upon him) used to be thirteen rak'ahs, that is, at night.

Umm al-Mu'mineen Aisha Siddiqa (may Allah be pleased with her) says that the Prophet Muhammad (peace and blessings be upon him) used to pray thirteen rak'ahs at night; among them were the Witr and the two (Sunnah) rak'ahs of Fajr.