Shulchan Aruch of Rabbi Shneur Zalman of Liadi, Volume 12: Choshen Mishpat

A person who genuinely wants to conduct his business with faith and honesty must guard his faith very carefully from any possible flaw. He must be as scrupulous as Rav Safra, (see Makhoth 24a) and he must “speak the truth in his heart” (Psalms 15:2). Even if he merely decided something in his heart, he must not change it later on. If he guards his

In both scenarios, according to Jewish law, you’re deceiving people by making them think you’ve given them something of value to you when you really haven’t. You’re thus getting credit for being generous that you don’t deserve.

As long as a person is reluctant to spend money on the mitzvot he performs, his mitzvot are deficient because they have not yet entered the category of true faith, which gives them their perfection. But when a mitzva is so precious in his eyes that he does not mind parting with his money and he spends liberally for the sake of the mitzva, this is c

person who has to have contact with non-Jews for business purposes must be very careful to see that his sanctity as a Jew is not affected. It is dangerously easy to get caught in their net, God forbid. He should always be steadfast and remind himself constantly of the holiness which is his heritage as a Jew. He should pray to God not to be influenc