قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ : " الصِّيَامُ جُنَّةٌ، فَإِذَا كَانَ يَوْمًا أَحَدُكُمْ صَائِمًا فَلا يَجْهَلْ وَلا يَرْفُثْ، فَإِنِ امْرُؤٌ قَاتَلَهُ أَوْ شَاتَمَهُ فَلْيَقُلْ : إِنِّي صَائِمٌ، إِنِّي صَائِمٌ "
And the Messenger of Allah, peace and blessings be upon him, said: "Fasting is a shield, so if any one of you is fasting on a day, he should neither behave ignorantly nor speak obscenely. So if someone fights with him or abuses him, then he (the fasting person) should say (in response): I am fasting, I am fasting."