Musnad Ahmad 658:176

Waki’ narrated to us, Sufyan narrated to us, from Abu Ishaq, who said: I heard Al-Bara’ ibn ‘Azib saying: When this verse was revealed: {And Allah has favored the mujahideen over those who remain behind with a great reward} [An-Nisa: 95], Ibn Umm Maktum came to him and said: O Messenger of Allah, what do you command me? For I am blind. He said: Then was revealed: {except those of disability} [An-Nisa: 95]. He said: Then the Prophet, peace and blessings of Allah be upon him, said: "Bring me the shoulder blade and the inkwell, or the tablet and the inkwell."