Muwatta Malik #150

Yahya related to me from Malik from al-Ala ibn Abd ar-Rahman ibn Yaqub from his father and Ishaq ibn Abdullah that they informed him that they heard Abu Hurayra say, "The Messenger of Allah, may Allah bless him and grant him peace, said, 'When the iqama is called for prayer, do not come to it running, but come with calmness. Pray what you catch and complete what you miss. You are in prayer as long as your aim is the prayer.' "