Allah said:

﴿ثُمَّ أَتِمُّواْ الصِّيَامَ إِلَى الَّيْلِ﴾

(...then complete your fast till the nightfall.)

This Ayah orders breaking the fast at sunset. It is recorded in the Two Sahihs that `Umar bin Al-Khattab said that Allah's Messenger said:

«إِذَا أَقْبَلَ اللَّيْلُ مِنْ ههُنَا، وَأَدْبَرَ النَّهَارُ مِنْ ههُنَا فَقَدْ أَفْطَرَ الصَّائِم»

(If the night comes from this direction (the east), and the day departs from that direction (the west), then the fasting person breaks his fast.)

It is reported that Sahl bin Sa`d As-Sa`idi narrated that Allah's Messenger said:

«لَا يَزَالُ النَّاسُ بِخَيْرٍ مَا عَجَّلُوا الْفِطْر»

(The people will retain goodness as long as they hasten in breaking the fast.)

Imam Ahmad recorded that Abu Hurayrah narrated that the Prophet said:

«يَقُولُ اللهُ عَزَّ وَجَلَّ: إِنَّ أَحَبَّ عِبَادِي إِلَيَّ أَعْجَلُهُمْ فِطْرًا»

(Allah the Exalted said, `The dearest among My servants to Me are those who hasten in breaking the fast the most.')

At-Tirmidhi recorded this Hadith and said that this Hadith is Hasan Gharib.