Volume 6, Book 60, Number 116:
Narrated Zaid bin Thabit: That the Prophet dictated to him: “Not equal are those of the believers
who sit (at home) and those who strive and fight in the Cause of Allah.”
Zaid added: Ibn Um Maktum came while the Prophet was dictating to me and said, “O Allah’s
Apostle! By Allah, if I had the power to fight (in Allah’s Cause), I would,” and he was a blind man. So
Allah revealed to his Apostle while his thigh was on my thigh, and his thigh became so heavy that I
was afraid it might fracture my thigh. Then that state of the Prophet passed and Allah revealed:–
“Except those who are disabled (by injury or are blind or lame etc).”