وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ أَبِي الزِّنَادِ، عَنِ الأَعْرَجِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏"‏ الصِّيَامُ جُنَّةٌ فَإِذَا كَانَ أَحَدُكُمْ صَائِمًا فَلاَ يَرْفُثْ وَلاَ يَجْهَلْ فَإِنِ امْرُؤٌ قَاتَلَهُ أَوْ شَاتَمَهُ فَلْيَقُلْ إِنِّي صَائِمٌ إِنِّي صَائِمٌ ‏"‏ ‏.‏

Yahya related to me from Malik from Abu'z Zinad from al-A'rajfrom Abu Hurayra that the Messenger of Allah, may Allah bless him andgrant him peace, said, "Fasting is a protection for you, so when youare fasting, do not behave obscenely or foolishly, and if any oneargues with you or abuses you, say, 'I am fasting. I am fasting.' " Translation Not Available

Book Ref: Muwatta Imam Malik Book 18 Hadith 690
Web Ref:  Muwatta Imam Malik Book 18 Hadith 57