Hadith on Fasting: A fasting person must give up bad behavior

Abu Huraira reported: The Messenger of Allah, peace and blessings be upon him, said, “When one of you wakes up in the morning for fasting, then he should not use obscene language or behave foolishly. If anyone abuses him or fights with him, he should say twice: Indeed, I am fasting.

Source: Ṣaḥīḥ Muslim 1151

Grade: Sahih (authentic) according to Muslim

عَنْ أَبِي هُرَيْرَةَ قَالَ قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ إِذَا أَصْبَحَ أَحَدُكُمْ يَوْمًا صَائِمًا فَلَا يَرْفُثْ وَلَا يَجْهَلْ فَإِنْ امْرُؤٌ شَاتَمَهُ أَوْ قَاتَلَهُ فَلْيَقُلْ إِنِّي صَائِمٌ إِنِّي صَائِمٌ

1151 صحيح مسلم  كتاب الصيام باب حفظ اللسان للصائم