Musnad Ahmad 30:2802

I read to Abd al-Rahman: Malik, and Ishaq narrated to us, he said: Malik narrated to me, from al-Ala’ ibn Abd al-Rahman ibn Ya’qub, from his father, in the hadith of Abd al-Rahman, and Ishaq Abu Abd Allah, that they both heard Abu Hurayrah say: The Messenger of Allah, peace and blessings of Allah be upon him, said: "When the prayer is called (iqamah), do not come to it while you are running, and come to it while upon you is tranquility. So whatever you reach, pray, and whatever you miss, complete it; for indeed, one of you is in prayer as long as he is intending the prayer."