Reference: Siyar A’laam an-Nubalaa – Volume 9, Page 157
Every night, Wakee’ ibn al-Jarraah would not sleep until he had read a third of the Qur.aan. Then, during the last [third] of the night he would stand in prayer and recite the al-Mufassal. He would then sit and engage in seeking forgiveness (al-istighfaar) until the arrival of Fajr.