Musnad Ahmad 487:6

Muhammad ibn Ja‘far narrated to us, Shu‘bah narrated to us, from Ya‘la ibn ‘Ata’, from Jabir ibn Yazid ibn al-Aswad, from his father, that he prayed the morning prayer with the Messenger of Allah (ﷺ) in Mina while he was a young boy. When the Messenger of Allah (ﷺ) finished praying, he noticed two men who had not prayed [with the congregation]. He called for them, and they were brought while their shoulders were trembling. He said to them, "What prevented you from praying with us?" They said, "We have already prayed in our dwellings." He said, "Do not do that. If you have prayed in your dwellings and then you reach the Imam while he has not prayed, then pray with him, for it will be a supererogatory (nafilah) prayer for you."