Abu Hurairah (RA):
Allah's Messenger (ﷺ) once came upon a heap of grain, and when he put his hand inside it, his fingers felt some dampness. So, he asked, "What is this, O owner of the grain?" He replied, "Rain had fallen on it, O Allah's Messenger." He said, "Why did you not put it (the damp part) on the top of the foodstuff so that people might see it? Whoever cheats has nothing to do with me."
[Reported by Muslim].