Musnad Ahmad 32:59

Muhammad ibn Fudayl narrated to us, Muhammad ibn Ishaq narrated to us, from al-Ala’ ibn Abd al-Rahman, who said: We entered upon Anas ibn Malik, I and a man from the Ansar, when we had prayed the Dhuhr prayer. He called the servant girl for ablution water. We said to him: "Which prayer are you praying?" He said: "The Asr." We said: "We have only just prayed the Dhuhr now." He said: "I heard the Messenger of Allah, peace and blessings of Allah be upon him, say: 'That is the prayer of the hypocrite; he leaves the prayer until, when it is at the horns of the devil, or between the horns of the devil, he prays it, not remembering Allah therein except a little.'"