Silsilat al-Ahadith al-Sahihah

Asim bin Damrah says: We asked Sayyiduna Ali (may Allah be pleased with him) about the voluntary prayers of the Prophet (peace and blessings be upon him) which he used to perform during the day. He said: Indeed, none of you has the strength to perform those prayers. We said: At least tell us, everyone will act according to his ability. He said: When the Prophet (peace and blessings be upon him) finished the Fajr prayer, he would refrain from performing (additional) prayers until the sun rose and became as high in the east as it is in the west at the time of Asr prayer. At that time, he (peace and blessings be upon him) would perform two rak‘ahs, then pause until the sun became as high in the east as it is in the west at the time of Zuhr. At that time, he (peace and blessings be upon him) would perform four rak‘ahs, then after the sun had declined, before Zuhr, he would perform four rak‘ahs, after Zuhr two, and before Asr four rak‘ahs. (In the four rak‘ah prayers) after every two rak‘ahs, he would pause and supplicate for peace for the close angels, the prophets, and the believing followers, and after the last rak‘ah, he would say the salam.