Thābit al-Bunānī narrated from Ibn Abī Laylā:
Ibn Umm Maktūm once said, “My Lord! Send down an excuse for me.”
So the verse was revealed: “except those who suffer a disability.”
Afterward he would take part in the campaigns, saying, “Hand me the banner, for I am blind—I cannot run away. Plant me between the two lines of battle.” (1)

ʿAbd al-Raḥmān ibn Abī al-Zinād narrated from his father, from Khārijah ibn Zayd, from his father, who said:
“I was beside the Prophet ﷺ when tranquility (sakīnah) overcame him; his thigh pressed against mine, and I never felt anything heavier. When the state lifted, he said to me, ‘Write.’
I wrote on a shoulder blade: ‘Those who remain behind among the believers are not equal to those who strive….’
ʿAmr ibn Umm Maktūm then stood up and said, ‘What of someone who is unable?’
His words had barely ended before tranquility again covered the Messenger of Allah ﷺ; when it was lifted he said, ‘Write: “except those who suffer a disability.”’
Zayd added, ‘Allah sent that clause down by itself, and I can still picture where it was attached at the split of the shoulder blade.’” (2)

Ibn Abī ʿArūbah narrated from Qatādah, from Anas:
“On the day of al-Qādisiyyah, ʿAbd Allah ibn Umm Maktūm carried a black standard and wore a coat of mail.” (3)