Maliks Muwatta Book 15, Hadith Number 46.
Section : Forbidding Prayer After Subh and After Asr.
Yahya related to me from Malik that al-Ala ibn Abd ar-Rahman said, “We visited Anas ibn Malik after dhuhr and he stood up and prayed asr. When he had finished his prayer, we mentioned doing prayers early in their time, or he mentioned it, and he said that he had heard the Messenger of Allah, may Allah bless him and grant him peace, say, the prayer of the hypocrites, the prayer of the hypocrites, the prayer of the hypocrites is that one of them sits until the sun becomes yellow and is between the horns of Shaytan, or on the horn of Shaytan, and then gets up and rattles off four rakas, hardly remembering Allah in them at all.'”