Maliks Muwatta Book 15, Hadith Number 48.
Section : Forbidding Prayer After Subh and After Asr.
Yahya related to me from Malik from Muhammad ibn Yahya ibn Habban from al Araj from Abu Hurayra that the Messenger of Allah, may Allah bless him and grant him peace, forbade prayer after asr until the sun had set, and prayer after subh until the sun had risen.