it was narrated in Saheeh al-Bukhaari (581) and Saheeh Muslim (831) that it is forbidden to pray after Fajr prayer until the sun has risen above the horizon to the height of a spear, at the time of noon when the sun is at its zenith, and after the time of Asr until the sun is fully set.

The Prophet (peace and blessings of Allaah be upon him) told us that the sun rises and sets between the two horns of a devil, at which time the kuffaar prostrate to it.