Musannaf Ibn Abi Shayba 3:4951

Ubayd Allah ibn Musa narrated to us, from Musa ibn Ubaydah, from Nafi, from Ibn Umar, that the Prophet (peace and blessings of Allah be upon him) forbade two prayers: a prayer after the dawn (Fajr) until the sun rises, and a prayer after the afternoon (Asr) until the sun sets.