The Prophet ﷺ said to him, "Lead your people in prayer."He said, "I replied, Messenger of Allah, I find something within myself."The Prophet ﷺ said, "Come closer."He seated me before him, then placed his palm on my chest between my breasts, and said, "Turn around."He then placed it on my back between my shoulders and said, "Lead your people in prayer. Whoever leads people in prayer should keep it short, for among them are the elderly, the sick, the weak, and those with pressing needs. But when one of you prays alone, let him pray however he wishes."
أن النبي ﷺ قال له: أم قومك. قال: قلت: يارسول 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 (468:186), from Muhammad bin Abdullah bin Numayr, who said, our father narrated to us, who said, Amr bin Uthman narrated to us, who said, Musa bin Talha narrated to us, who said, Uthman bin Abu As Thaqafi narrated to me, and he related it.