Mukhtar bin Fulful said: I asked Anas bin Malik (may Allah be pleased with him) about prayer after Asr, and he said: Sayyiduna Umar (may Allah be pleased with him) used to strike people for praying after Asr. He said: In the time of the Prophet (peace and blessings be upon him) we used to pray two rak'ahs after sunset, before the Maghrib prayer. The narrator said: I said: Did the Prophet (peace and blessings be upon him) pray two rak'ahs? He said: The Prophet (peace and blessings be upon him) used to see us praying (them), and he neither ordered us nor forbade us.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4496