Musnad Ahmad 30:2707

Hajjaj narrated to us, he said: Layth narrated to us, he said: ‘Uqayl narrated to me, from Ibn Shihab, that he said: Abu Salamah ibn ‘Abd al-Rahman ibn ‘Awf informed me that he heard Abu Hurayrah saying: The Messenger of Allah (peace and blessings of Allah be upon him) said: "When the prayer is established, do not come to it running, but come to it walking, upon you is tranquility. So whatever you catch, pray, and whatever you miss, complete it."