The Messenger of Allah ﷺ said, "When it is the day of fasting for any of you, let him not engage in obscene speech or behave ignorantly. If anyone behaves ignorantly toward him, let him say, 'I am a man who is fasting.'"
حدثنا محمد بن بكر أخبرنا إسرائيل عن أبي حصين عن أبي صالح
قال رسول الله ﷺ إذا كان يوم صوم أحدكم فلا يرفث ولا يجهل فإن جهل عليه أحد فليقل إني امرؤ صائم
Its isnad is sahih. Abu Husayn, with fatha on the ha and kasra on the sad, both unvoiced, is Uthman bin Asim, previously mentioned at 1024 and 6826, and the hadith is an abridged version of 7679.