Yahya related to me from Malik from Zayd ibn Aslam from Ata ibnYasar from Abdullah as-Sunabihi that the Messenger of Allah, may Allahbless him and grant him peace, said, "The sun rises and with it is ahorn of Shaytan and when the sun gets higher the horn leaves it. Thenwhen the sun reaches the meridian the horn joins it and when the sundeclines the horn leaves it, and when the sun has nearly set it joinsit again." The Messenger of Allah, may Allah bless him and grant himpeace, forbade prayer at these times.
USC-MSA web (English) reference: Book 15, Hadith 44
Arabic reference: Book 15, Hadith 516