سنن النسائي

It was narrated from Abu Hurairah that the Messenger of Allah (ﷺ) said: "There are three to whom Allah will not speak on the Day of Resurrection, or will He look at them, or sanctify them and theirs will be a painful torment: A man who has surplus water when traveling but he withholds it form a wayfarer; a man who swears allegiance to an imam for worldly gains, and if he gives him what he wants he is loyal to him but if he does not give him anything he is not loyal to him: and a man who sells a man his product after 'Asr, swerving by Allah that he bought it for such and such a price, and the other believes him."