(a) It is narrated from Abu Yunus, the freed slave of the Mother of the Believers, Sayyidah Aishah (may Allah be pleased with her): She ordered me to write a copy of the Qur'an (mushaf) for her, then she said: "When you reach this verse, 'Guard the prayers, especially the middle prayer' [Surah al-Baqarah: 238], let me know." When I reached that place, I informed her, and she dictated to me: "Guard the prayers, especially the middle prayer, and the Asr prayer as well, and stand before Allah in devout obedience." Sayyidah Aishah (may Allah be pleased with her) said: "I heard this from the Messenger of Allah (peace and blessings be upon him)."
(b) In this there is evidence that the Asr prayer is one prayer and the middle prayer is another.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2173