Sunan Ibn Majah, Chapter: The Chapters of Establishing the Prayer and the Sunnah Regarding Them

"I came to the Messenger of Allah (saw) and said: 'Is there any time that is more beloved to Allah than another?' He said: 'Yes, the middle of the night, so pray as much as you want until dawn comes. Then refrain from praying until the sun has risen, and as long as it looks like a shield until it becomes apparent. Then pray as much as you want until a pole stands on its shadow (i.e., noon), then refrain from praying until it has crossed the zenith, for Hell is heated up at midday. Then pray as much as you want until you pray 'Asr, then refrain from praying until the sun has set, for it sets between the two horns of Satan and it rises between the two horns of Satan.'" Hasan