The sun rises and with it is a horn of Shaytan and when the sun gets higher the horn leaves it. Then when the sun reaches the meridian the horn joins it and when the sun declines the horn leaves it, and when the sun has nearly set it joins it again." The Messenger of Allah, may Allah bless him and grant him peace, forbade prayer at these times.

Malik :: Book 15 : Hadith 15.10.44