William Muir,
The Caliphate: Its Rise, Decline and Fall…
“ He followed the army to Syria, and there, honoured for the office he had so long discharged at Medina, lived in retirement. The Chief citizens of Damascus now petitioned 'Omar that on this last occasion, Bilal should be asked once more to perform the Call to Prayer. The aged man consented, and as from the top of the Great Mosque the well-known voice arose clear and loud with the accustomed cry, the whole assembly, recalling vividly the Prophet at daily prayers, was melted into tears, and strong warriors with 'Omar at their head, lifted up their voices and sobbed aloud. ”
