Musnad Abi Ya'la 1798 — Sayyiduna Ubayy bin Ka'b was leading

It is narrated from Sayyiduna Jabir bin Abdullah (may Allah be pleased with him) that Sayyiduna Ubayy bin Ka'b (may Allah be pleased with him) was leading the people of Quba' in prayer when he began reciting a long surah. A young man of the Ansar joined him in the prayer. When he heard that he had begun a long surah, the young man left his prayer and went apart, because he wanted to tend to his camel with which he carried water. When Sayyiduna Ubayy bin Ka'b (may Allah be pleased with him) finished the prayer, the people told him that so-and-so had left the prayer and gone. At this Sayyiduna Ubayy (may Allah be pleased with him) became angry and came to the Prophet (peace and blessings be upon him) to complain about the young man, while the young man also came to him (peace and blessings be upon him) to complain about him. On hearing this the Prophet (peace and blessings be upon him) became so angry that signs of anger were clearly seen on his blessed face. Then he (peace and blessings be upon him) said: "Among you are some who drive people away (from the religion). So when you lead (the prayer), keep it brief, for behind you among the followers are the weak, the old, the sick and the needy."