63:4 It is forbidden to deceive others through one's words, even if one doesn't cause any financial loss. This applies equally to non-Jews. For example, one may not sell a non-Jew the meat of an animal that died under the false pretense that it was ritually slaughtered. If a person sells an object that has some defect, he must inform the buyer of the defect even if the price already reflects the item's value. It is not considered deceptive to give a person a gift that has a defect.
63:5 One should not extend an invitation to a person whom he is confident will not accept. The same is true with offering a gift to a person he knows will not accept it. Any situation where a person says one thing and means another is forbidden, such as honoring a person insincerely. Rather, what one says should always be consistent with how he feels. A person should always speak truthfully, with the proper intentions.