Aḥmad ibn Yaḥyá al-Balādhurī, The Origins of the Islamic State (1916)
“ Rustam, snorting with anger, said, "By the sun and by the moon, the day will not break to-morrow before we kill you all." "No strength and no force but in Allah," answered al-Mughîrah, and departed riding a lean horse with a sword broken at its edge and wrapped up in rags. [5] ʿAmr and al-Ashʿath interview Rustam. ʿUmar wrote to Saʿd instructing him to send to the magnate of the Persians a delegation to invite him to Islâm. Accordingly, Saʿd sent ʿAmr ibn-Maʿdikarib az-Zubaidi and al-Ashʿath ibn-Ḳais al-Kindi at the head of a delegation. ”
