Musnad Ahmad 30:1901

'Affan narrated to us, Abu 'Awanah narrated to us, 'Umar ibn Abi Salamah narrated to us, from his father, from Abu Hurayrah, from the Prophet (peace and blessings of Allah be upon him), who said: "When one of you hears the iqamah, let him come to it with tranquility. Whatever you catch, pray it, and whatever you miss, complete it."