The Messenger of Allah ﷺ passed a man who was selling grain. He asked him: How are you selling? He informed him. Revelation them came down to him saying: "Put your hand into it." So he put his hand into it, and felt that it was damp. The Messenger of Allah ﷺ then said: "He who deceives has nothing to do with us." (Using translation from Abū Dāʾūd 3452)
أَنَّ رَسُولَ اللهِ ﷺ مَرَّ بِرَجُلٍ يَبِيعُ طَعَامًا فَسَأَلَهُ كَيْفَ تَبِيعُ؟ فَأَخْبَرَهُ فَأُوحِيَ إِلَيْهِ أَدْخِلْ يَدَكَ فِيهِ فَأَدْخَلَ يَدَهُ فَإِذَا هُوَ مَبْلُولٌ فَقَالَ رَسُولُ اللهِ ﷺ لَيْسَ مِنَّا مَنْ غَشَّ