Musnad Ahmad 30:340

'Abd al-Malik ibn 'Amr narrated to us, 'Ali—meaning Ibn al-Mubarak—narrated to us, from Yahya—meaning Ibn Abi Kathir—from Abu Salamah, Abu Hurairah narrated to me, that the Prophet, peace and blessings of Allah be upon him, said: "Whoever prays one rak'ah of the morning prayer before the sun rises, then he has not missed it. And whoever prays one rak'ah of the afternoon prayer before the sun sets, then he has not missed it."