The Prophet ﷺ said to him, "Lead your people in prayer."He replied, "Messenger of Allah, I feel something within myself."The Prophet ﷺ said, "Come closer." He sat me down in front of him, placed his palm on my chest between my breasts, then said, "Turn around," and placed it on my back between my shoulders. Then he said, "Lead your people in prayer. Whoever leads people in prayer should keep it brief, for among them are the elderly, the sick, the weak, and those with needs to attend to. But when one of you prays alone, let him pray however he wishes."
أن النبي ﷺ قال له: أم قومك قال قلت: يا رسول الله! إني أجد في نفسي شيئا، قال: اذنه فجلسني بين يديه، ثم وضع كفه في صدري بين ثديي. ثم قال: تحول فوضعها في ظهري بين كتفي، ثم قال: أم قومك، فمن أم قوما فليخفف، فإن فيهم الكبير، وإن فيهم المريض، وإن فيهم الضعيف، وإن فيهم ذا الحاجة، وإذا صلى أحدكم وحده فليصل كيف شاء.
Muslim narrated it in the Book of Prayer (468) from Muhammad bin Abdullah bin Numayr, who said, our father narrated to us, Amr bin Uthman narrated to us, Musa bin Talha narrated to us, Uthman bin Abu As narrated to me, and he mentioned it. He also narrated it through another route from Saeed bin Musayab, who said, Uthman bin Abu As related, saying, "The last thing the Messenger of Allah ﷺ instructed me was, 'When you lead people in prayer, keep the prayer light for them.'" That was when he appointed him governor over Taif, as in the report of Ibn Majah (987) through Mutarrif bin Abdullah bin Shikhir, from Uthman bin Abu As.In the hadith of Abu Dawud (531), he asked the Prophet ﷺ to appoint him as the imam for his people, and the Prophet said, "You are their imam, but follow the pace of the weakest among them."For more, see the Book of adhan.