Musnad Ahmad 658:181

'Abd al-Rahman narrated to us, from Shu'bah, from Abu Ishaq, from al-Bara', who said: And Ibn Ja'far narrated to us, Shu'bah narrated to us, from Abu Ishaq, that he heard al-Bara' say: When the verse was revealed: "Those of the believers who sit [at home] are not equal [to those who strive in the cause of Allah]," the Messenger of Allah, peace and blessings of Allah be upon him, called Zayd, and he brought a shoulder blade and wrote it down. Then Ibn Umm Maktum complained of his blindness, and so it was revealed: "Those of the believers who sit [at home], other than those who have a disability, are not equal [to those who strive in the cause of Allah]."