Sayyiduna Abu Hurayrah (may Allah be pleased with him) narrates from the Prophet (peace and blessings be upon him) that he (peace and blessings be upon him) said: "The middle prayer is the Asr prayer."
It was narrated like this with this chain; others differed from him and narrated it from al-Taymi as mawquf (stopping) at Abu Hurayrah.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2165