Musannaf Ibn Abi Shaybah 6806 — One who prays at home and then finds

Sayyiduna Yazid bin al-Aswad al-Amiri (may Allah be pleased with him) said: I was present with the Messenger of Allah (peace and blessings be upon him) at his Hajj. I prayed the Fajr prayer with him in Masjid al-Khayf. When he had completed the prayer and turned away from the qiblah, there were two men at the back of the people who had not prayed with him. He said: "Bring the two of them to me." When they were brought before him, both of them were trembling. He asked them: "Why did you not pray with us?" They both said: "O Messenger of Allah, we had already prayed in our camps." He (peace and blessings be upon him) said: "Do not do that. When you have prayed in your camps and then come to a mosque where the prayer is being held, pray with them as well. That prayer will be voluntary for you."