The initial compilation of the Qur'an into a written manuscript was commissioned by which Caliph, following the advice of Umar ibn al-Khattab?

After the Battle of Yamama (633 CE), in which a large number of Qur'an memorizers (Huffaz) were killed, Umar ibn al-Khattab advised Caliph Abu Bakr al-Siddiq to compile the Qur'an into a single written volume to preserve it. Abu Bakr accepted this advice and assigned Zayd ibn Thabit to lead the compilation. This manuscript was later kept with Hafsah bint Umar and served as the basis for Uthman's standardized copies.