Sayyiduna Samurah (may Allah be pleased with him) says: The Messenger of Allah (peace and blessings be upon him) used to order us to pray at whatever hour we wished of the night and day, except that he (peace and blessings be upon him) ordered us to avoid the rising and setting of the sun, and he said: "Satan sets with it, and rises with it when it rises."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6977