It was narrated that 'Aishah said that the Prophet said:"Fasting is a shield against the Fire. Whoever starts the day of fasting, let him not act in an ignorant manner during that day. If anyone treats him in an ignorant maner, let him not insult him or curse him, rather let him say: "I am fasting.' By the One in whole hand is the soul of Muhammad, the smell that comes from the mouth of a fasting person is better before Allah than the fragrance of musk."
أَخْبَرَنَا مُحَمَّدُ بْنُ يَزِيدَ الآدَمِيُّ، قَالَ حَدَّثَنَا مَعْنٌ، عَنْ خَارِجَةَ بْنِ سُلَيْمَانَ، عَنْ يَزِيدَ بْنِ رُومَانَ، عَنْ عُرْوَةَ، عَنْ عَائِشَةَ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " الصِّيَامُ جُنَّةٌ مِنَ النَّارِ فَمَنْ أَصْبَحَ صَائِمًا فَلاَ يَجْهَلْ يَوْمَئِذٍ وَإِنِ امْرُؤٌ جَهِلَ عَلَيْهِ فَلاَ يَشْتِمْهُ وَلاَ يَسُبَّهُ وَلْيَقُلْ إِنِّي صَائِمٌ وَالَّذِي نَفْسُ مُحَمَّدٍ بِيَدِهِ لَخُلُوفُ فَمِ الصَّائِمِ أَطْيَبُ عِنْدَ اللَّهِ مِنْ رِيحِ الْمِسْكِ " .
Nesai
The Book of Fasting • Hadith 2234