Abu Hurairah (May Allah be pleased with him) reported:
The Messenger of Allah (Sallallahu Alaihi Wasallam) said,
"Allah the Exalted and Majestic said:
`Every act of the son of Adam is for him,
except As-Siyam (the fasting) which is (exclusively) for Me,
and I will reward him for it.' Fasting is a shield."
When anyone of you is observing fast,
he should neither indulge in obscene language
nor should he raise his voice;
and if anyone reviles him or tries to quarrel with him,
he should say: `I am fasting.'
By Him in Whose Hand the soul of Muhammad is,
the breath of one observing Saum is sweeter to Allah
than the fragrance of musk.
The one who fasts, experiences two joys:
he feels pleasure when he breaks the fast.
He is joyful by virtue of his fast when he meets his Rubb.''
Ref:[Al-Bukhari and Muslim].
"Khuluf'', is the smell that comes from the mouth of person who observes Saum.
It results from the thirst and hunger which he has to suffer during the Saum.
The Hadith not only tells us the merits of Saum but also brings into focus
the true significance of it. Saum is not thus mere abstention from food, drink and
sexual intercourse, but also keeping away from all evils and vices and embracing virtues.