Musnad Ahmad 937:18

'Abd al-Razzaq narrated to us, Sufyan informed us, from Ayyub, from Abu al-'Aliyah, who said: Ubayd Allah ibn Ziyad delayed the prayer, so I asked 'Abd Allah ibn al-Samit. He struck my thigh and said: I asked my intimate friend, Abu Dharr, and he struck my thigh and said: I asked my intimate friend—meaning the Prophet, peace and blessings of Allah be upon him—and he said: "Pray at its appointed time. If you catch the prayer [with the congregation], then pray with them, and do not say: 'I have already prayed, so I will not pray.'"