From Sahih Bukhari (Hadith 4592):
Narrated Zaid bin Thabit:That the Prophet (ﷺ) 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 (ﷺ) 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 (ﷺ) passed and Allah revealed:-- "Except those who are disabled (by injury or are blind or lame etc)
Reference: Bukhari 4592