Sahih Muslim, Chapter: Faith (Kitab Al Iman)

Abu Huraira narrated on the authority of Abu Bakr that the Messenger of Allah (may peace be upon him) said: Three are the persons with whom Allah would neither speak on the Day of Resurrection, nor would He look towards them, nor would purify them (from sins), and there would be a tormenting chastisement for them: a person who in the waterless desert has more water (than his need) and he refuses to give it to the traveller and a person who sold a commodity to another person in the afternoon and took an oath of Allah that he had bought it at such and such price and he (the buyer) accepted it to be true though it was not a fact, and a person who pledged allegiance to the Imam but for the sake of the world (material gains). And if the Imam bestowed on him (something) out of that (worldly riches) he stood by his allegiance and if he did not give him, he did not fulfil the allegiance.