The Messenger of Allah (may Allah’s peace and blessings be upon him) appointed Ibn Umm Maktūm as his successor to lead the people in prayer, and he was blind

The Prophet (may Allah's peace and blessings be upon him) appointed Ibn Umm Maktūm as his successor in Madīnah as he went on some journeys. This is because Ibn Umm Maktūm was more qualified than others. He was one of the first people to accept Islam, and he was also a scholar and a skilled reciter of the Qur’an. Therefore, he deserved to be put in a leadership position. He would issue Islamic verdicts, judge between people, and manage all the affairs of Madīnah while the Messenger was absent. This is proven by a narration in which Ibn ‘Abbās (may Allah be pleased with him) reported: “The Prophet (may Allah's peace and blessings be upon him) appointed Ibn Umm Maktūm as his successor in prayer and the other affairs of Madīnah.” [At-Tabarāni]
In another narration: “The Prophet (may Allah's peace and blessings be upon him) appointed Ibn Umm Maktūm as his successor in Madīnah twice.” [Abu Dawūd]