Umar, also spelled Omar (عمر بن الخطاب‎ ʻUmar ibn al-Khaṭṭāb, "Umar, Son of Al-Khattab"; c. 584 CE – 3 November 644 CE), was a senior companion of the Prophet Muhammad. He was appointed by Abu Bakr to succeed him and occupied the position of caliph till his death.

Uthman ibn Affan (Arabic: عثمان بن عفان‎, romanized: ʿUthmān ibn ʿAffān), also known in English by the Turkish and Persian rendering Osman (579/583 – 17 June 656), was a companion of the Prophet Muhammad and the third person to occupy the seat of caliphate after the Prophet.

William C. Chittick (born 1943) is a philosopher, writer, translator and interpreter of classical Islamic philosophical and mystical texts. He is best known for his work on Rumi and Ibn 'Arabi, and has written extensively on the school of Ibn 'Arabi, Islamic philosophy, and Islamic cosmology.