The Messenger of Allah ﷺ passed by a heap of food and put his hand into it. His fingers came out moist, so he asked, "What is this, owner of the food?"The man replied, "It was struck by rain, Messenger of Allah."The Prophet ﷺ said, "Why did you not place it on top of the food so that people could see it? Whoever deceives is not one of me."
أن رسول الله ﷺ مر على صبرة طعام، فأدخل يده فيها، فنالت أصابعه بللا، فقال: ما هذا يا صاحب الطعام؟ قال: أصابته السماء، يا رسول الله. قال: أفلا جعلته فوق الطعام كي يراه الناس. من غش فليس مني.
Muslim narrated it in the Book of Faith (102), through several routes, from Ismail bin Jafar, who said, Ala informed me, from his father, from Abu Hurairah, and he mentioned something similar. Tirmidhi narrated it (1315) through this same route, and said, hasan sahih. Imam Ahmad narrated it (7292), and from him Abu Dawud (3492), from Sufyan, from Ala, and it states there, "So it was revealed to him, 'Put your hand into it.' He put his hand in, and found it wet. The Messenger of Allah ﷺ then said, 'Whoever cheats is not one of us.'" Ibn Majah narrated it (2224) through another route from Sufyan, but did not mention the story of the revelation.