 Complete the following phrase:  As a child, during the reign of Caliph Umar in 636, Ibn al-Zubayr may have been present with his father at the Battle of Yarmouk against the Byzantines in Syria. He was also present with his father in Amr ibn al-Ass campaign against Byzantine Egypt in 640. In 647, Ibn al-Zubayr distinguished himself in the Muslim conquest of Ifriqiya North Africa under the commander Abd Allah ibn Sad. During that campaign, Ibn al-Zubayr discovered a vulnerable point in the battle lines of the Byzantine defenders and slew their patrician, Gregory. He was lauded by Caliph Uthman and issued a victory speech, well known for its eloquence, upon his return to Medina. Later, he joined Said ibn al-As in the latters offensive in northern Iran in 650. Uthman appointed Ibn al-Zubayr to the commission charged with the recension of the Quran. During the 