Musnad Ahmad 938:57

Makki narrated to us, Abdullah bin Sa'id bin Abi Hind narrated to us, from Abu an-Nadr, from Busr bin Sa'id, from Zayd bin Thabit al-Ansari, who said: The Messenger of Allah (peace and blessings of Allah be upon him) partitioned off a small room in the mosque. The Messenger of Allah (peace and blessings of Allah be upon him) would come out at night and pray in it. Some men prayed along with him, following his prayer. They would come to him every night. Then, on one of the nights, the Messenger of Allah (peace and blessings of Allah be upon him) did not come out to them. They cleared their throats and raised their voices. He said: So the Messenger of Allah (peace and blessings of Allah be upon him) came out to them in anger. He said to them: "O people, your behavior continued until I thought it would be made obligatory upon you. So, you must pray in your houses, for the best prayer of a person is in his house, except for the obligatory prayer."