(45) باب تَعْجِيلِ الإِفْطَارِ
Narrated Ibn Abi `Aufa:
I was with the Prophet (ﷺ) on a journey, and he observed the fast till evening. The Prophet (ﷺ) said to a man, "Get down and mix Sawiq with water for me." He replied, "Will you wait till it is evening?" The Prophet said, "Get down and mix Sawiq with water for me; when you see night falling from this side, the fasting person should break his fast."
Reference: Sahih al-Bukhari 1958
In-book reference: Book 30, Hadith 65
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 3, Book 31, Hadith 179