Reference: Siyar A’laam an-Nubalaa v8 p136
said:
The people of Egypt would disparage ‘Uthmaan ibn ‘Affaan, until al-Layth ibn Sa’d emerged from [amongst] them and spoke to them about his virtues, and so they refrained.
And the people of Hums would disparage ‘Ali [ibn Abi Taalib], until Ismaa’eel ibn ‘Ayyaash emerged from [amongst] them and spoke to them about the virtues of ‘Ali, and so they refrained from that.
