the first person to institute a system of dating was ʿUmar ibn al-Khaṭṭāb—may Allah be pleased with him—two and a half years after he became caliph. Acting on the counsel of ʿAlī—may Allah be pleased with him—he dated the document “the sixteenth year after the Hijra.”

In that same year he sent Rubayʿ ibn al-Afkal to fight the people of Mosul.

Year Seventeen (17 AH):
It is said that the previously mentioned battle of Jalūlāʾ took place this year.

During it, ʿUmar—may Allah be pleased with him—set out for Sargh, appointing Zayd ibn Thābit as acting governor of Medina. When he learned that plague had broken out in Syria, he turned back after ʿAbd al-Raḥmān ibn ʿAwf related to him the Prophet’s—peace and blessings be upon him—teaching concerning plague.

That same year ʿUmar enlarged the Prophet’s Mosque, rebuilding it in the same manner it had been during the Prophet’s lifetime.

A severe drought also struck the Ḥijāz that year, later called “the Year of al-Murādah.” ʿUmar led the rain-seeking prayer on behalf of the people, invoking Allah through al-ʿAbbās, the Prophet’s uncle—may Allah be pleased with him.

In that year ʿUmar wrote to Abū Mūsā al-Ashʿarī, appointing him governor of Basra and ordering him to advance into the districts of Ahwāz. Abū Mūsā set out, leaving ʿImrān ibn Ḥuṣayn in charge of Basra, and he took Ahwāz partly by treaty and partly by force. ʿUmar assessed its tribute at ten million four hundred thousand dirhams. During his own term of office, Ziyād strove to separate what had been taken by force from what had been secured by treaty, but he was unable to do so.

Khalīfah said: In that same year Abū Bakrah and Nāfiʿ—the sons of al-Ḥārith—and Shibl ibn