Yahya related to me from Malik from Hisham ibn Urwa that hisfather said that the Messenger of Allah, may Allah bless him and granthim peace, used to say, "Delay the prayer when the edge of the sunappears until it is completely in view, and delay the prayer when theedge of the sun is disappearing until it has completely disappeared." (FR)
USC-MSA web (English) reference: Book 15, Hadith 45 (FR)
Arabic reference (FR): Book 15, Hadith 517 (FR)