Musnad Ahmad 30:676

'Abd al-Razzaq narrated to us, Sufyan narrated to us, from Sa'd ibn Ibrahim, 'Umar ibn Abi Salamah narrated to us, from his father, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever among you comes to the prayer, let him come to it with dignity and tranquility. Let him pray what he catches, and let him complete what he missed."