Sayyidah Aishah (may Allah be pleased with her) said that Umar (may Allah be pleased with him) was mistaken; he (peace and blessings be upon him) had only forbidden "that one should wait for the rising or setting of the sun."
She said that, and Allah knows best, because she had seen the Messenger of Allah (peace and blessings be upon him) pray the two rak'ahs after Asr; these two, as is established from her and from Umm Salamah, were a making-up of missed prayer, and when he (peace and blessings be upon him) did a deed he kept it up. As for the prohibition, it is established from the Prophet (peace and blessings be upon him) through Umar and others, as has preceded.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4381