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).
Sahih al-Bukhari Book 65, Hadith 114
← Previous Hadith Regarding the Verse: "And say not to anyone who offers you peace (by accepting Islam), You are not a believer." There was a man amidst his sheep. The Muslims pursued him, and he said (to them) "Peace be on you." But they killed him and took over his sheep. Thereupon Allah revealed in that concern, the above Verse up to:-- "...seeking the perishable good of this life." (4.94) i.e. those sheep.

Sahih al-Bukhari Book 65, Hadith 113 Next Hadith → When the Verse:-- "Not equal are those of the believers who sit (at home)" (4.95) was revealed, Allah Apostle called for Zaid who wrote it. In the meantime Ibn Um Maktum came and complained of his blindness, so Allah revealed: "Except those who are disabled (by injury or are blind or lame..." etc.) (4.95)

Sahih al-Bukhari Book 65, Hadith 115