Sahih Al Bukhari – Book of Times Of The Prayers

Volumn 001, Book 010, Hadith Number 557.
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Narated By Hisham's father : Ibn 'Umar said, "Allah's Apostle said, 'Do not pray at the time of sunrise and at the time of sunset.' " Ibn 'Umar said, "Allah's Apostle said, 'If the edge of the sun appears (above the horizon) delay the prayer till it becomes high, and if the edge of the sun disappears, delay the prayer till it sets (disappears completely).' "