Musnad Ahmad 30:2973

Waki’ and ‘Abd al-Rahman narrated to us, they said: Sufyan narrated to us, the meaning, from Sa’d ibn Ibrahim, from ‘Umar ibn Abi Salamah, from his father, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "When you come to the prayer, come to it with dignity and tranquility. Whatever you catch, pray, and whatever you miss, complete."