Musnad Abu Ya'la al-Mawsili 243:79

On the authority of Abu Musa, he said: I and my companions who arrived with me on the ship were staying in Baqi' Buthan, and the Messenger of Allah (peace and blessings of Allah be upon him) was in Medina. A group of them would take turns with the Messenger of Allah (peace and blessings of Allah be upon him) at the time of the Isha prayer every night. Abu Musa said: We encountered the Messenger of Allah (peace and blessings of Allah be upon him)—I and my companions—while he was occupied with some of his affairs, so he delayed the prayer until the night had deepened. Then the Messenger of Allah (peace and blessings of Allah be upon him) came out. When he finished his prayer, he said to those who were present: "Take your time. Rejoice, for it is among the blessings of Allah upon you that there is no one among the people who prays this prayer except you," or he said, "No one has prayed at this hour except you"—he did not know which of the two phrases he said. Abu Musa said: So we returned happy because of what we heard from the Messenger of Allah (peace and blessings of Allah be upon him).