Sahih Bukhari

Narrated Abu Bakr bin `Uthman bin Sahl bin Hunaif:that he heard Abu Umama saying: We prayed the Zuhr prayer with `Umar bin `Abdul `Aziz and then went to Anas bin Malik and found him offering the `Asr prayer. I asked him, ""O uncle! Which prayer have you offered?"" He said 'The `Asr and this is (the time of) the prayer of Allah's Apostle which we used to pray with him