From Sahl ibn Sa’d as Saa’idee radi Allaahu ‘anhu who said that the Messenger of Allaah sall Allaahu ‘alaihi wa sallam said:

“The people will not cease to be upon goodness as long as they hasten to break the fast.”

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The Shaykh Muhammad ibn Saalih al ‘Uthaymeen rahimahullaah commented:

All goodness is contained in following the Islamic Legislation and in restricting oneself to it, without going to excess or falling short.

And in this hadeeth, Sahl ibn Sa’d radi Allaahu ‘anhu informs that the Prophet sall Allaahu ‘alaihi wa sallam told (us) that the people will continue upon goodness and righteousness in their religion if they restrict themselves to (staying within) the Islamically legislated limits for their fasting and their breaking the fast.

So be prompt with breaking the fast after the setting of the sun – which is the (legislated) limit for the fasting – just as Allaah, the Most High, said:

Then complete your fasting till the nightfall…
Soorah al Baqarah (2) aayah 187

And the night enters with the setting of the sun.

(taken from Sh Uthaymeen’s explanation of ‘Umdat-ul-Ahkaam
translated by Nasser ibn Najam)