We have explained the prohibition of genebat da'at, i.e., when I falsely pretend that I care or I want to help, just to benefit from leaving a positive impression in somebody else mind. Our Rabbis classified these actions as "stealing peoples' mind".
A typical example: If one of my friends is preparing a party or an event for which manpower is required, and my help is definitely needed. And, for whatever the reason might be, I don't come to help. But when I estimate that everything is done and ready and my help is not needed anymore, I come to my friend's house to offer my help. And when my friend tells me that everything is already done, I pretend as if I'm sorry and regret that I can not be of help... For me, it might look like a win/win situation: I have not helped, and I still enjoy the benefit of having left a positive impression on my friend as if I had really helped him!
The Tora condemns this type of cynical attitude and considers it a form of "stealing".
There are some cases, however, in which one can sincerely be offering his or her help, even though one knows that his offer will be refused. If for example, I come to my friend's house and I see that he has an unexpected guest or event, etc. and then I sincerely offer my help, not to cause a false impression, but to show that I care, knowing that my empathy will make my friend feeling good, then it is absolutely valid.
In other words, the issue of genebat da'at depends on one's intention and cannot be judged by a third party based just on the facts at sight. genebat da'at pertains to a category of actions that are judged only between oneself and God.
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