Ibn ‘Umar (may Allah be pleased with him) reported that the Messenger of Allah (may Allah’s peace and blessings be upon him) said: "When the edge of the sun rises, avoid prayer until it becomes prominent; and if the edge of the sun disappears, avoid prayer until it sets. And do not offer your prayer at the time of sunrise or sunset, for it rises between two horns of a devil – or the devil."
In this Hadīth, the Prophet (may Allah's peace and blessings be upon him) commands us to not offer prayer when the edge of the sun that appears first at sunrise shows until the entire sun rises and becomes high in the sky. We should also avoid prayer when the edge of the sun disappears until the sun has completely set. The Prophet has forbidden us from praying at times of sunrise and sunset because the sun rises and sets between the two horns of the devil, i.e. the two sides of his head. This is because the devil faces the sun when it rises so that it rises between his two horns, so that he becomes a Qiblah for those who prostrate themselves before the sun. The same happens during sunset. Therefore, we are prohibited from praying at these times to avoid resembling those people in their false worship.