Narrated Ibn `Umar: A man came to the Prophet and said, "I am often betrayed in bargaining." The Prophet advised him, "When you buy something, say (to the seller), 'No deception." The man used to say so afterwards.

Narrated Al-Mughira bin Shu`ba: The Prophet said, "Allah has forbidden for you, (1) to be undutiful to your mothers, (2) to bury your daughters alive, (3) to not to pay the rights of the others (e.g. charity, etc.) and (4) to beg of men (begging). And Allah has hated for you (1) vain, useless talk, or that you talk too much about others, (2) to ask too many questions, (in disputed religious matters) and (3) to waste the wealth (by extravagance).