Narrated Abu Hurairah (radiyallaahu-anahu) that the Messenger of Allaah (sallal-laahu-alayhi-wasallam) said that Allaah said: ‘’All the deeds of Adam’s sons (people) are for them, except Saum (fasting) which is for Me, and I will give the reward for it.’ Observing saum (fast) is a shield or protection (from the Hell-fire and from committing sins). If one of you is observing Saum (fast), he should avoid sexual relation with his wife and quarrelling, and if somebody should fight or quarrel with him, he should say, ‘I am observing Saum (fast).’ By Him in Whose Hands my soul is, the smell coming out from the mouth of a fasting person is better before Allah than the smell of musk. There are two pleasures for the person observing Saum, one at the time of Iftaar (breaking his fast), and the other at the time when he will meet his Lord; then he will be pleased because of his Saum (fasting).’’

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[Bukhaari. Number: 1094]