عَنْ أَبِي هُرَيْرَةَ رَضِيَ اللَّهُ عَنْهُ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ: ((إِذَا كَانَ يَوْمُ صَوْمِ أَحَدِكُمْ فَلَا يَرْفُثْ يَوْمَئِذٍ وَلَا يَصْخَبْ، فَإِنْ سَابَّهُ أَحَدٌ أَوْ قَاتَلَهُ أَحَدٌ فَلْيَقُلْ إِنِّي امْرُؤٌ صَائِمٌ))
Sayyiduna Abu Huraira (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) said: When any one of you is fasting, he should neither use foul language nor raise his voice; if someone abuses him or fights with him, he should simply reply, "I am fasting."