question #1 Sahih al-Bukhari 1958, Book 30, Hadith 65 : What is the significance of breaking the fast as soon as night falls in Islamic tradition?

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.”