NUM353 The sixth category [of liars] consists of those who assure their fellow man of some benefit, so assuring him until he is implicitly trusted. This trust should not be violated, and if one is false in this, he incurs greater punishment than the aforementioned falsifier who only spoke in general terms, being like the breaker of a covenant. And if one told his neighbor that he would give him a small gift, even though he used no terms of assurance, about this our Rabbis have stated (Bava Metzia 49a): "Retracting one's words constitutes a breach of faith," for his neighbor relies upon him and trusts him, since the gift in question is only a small one. And if the one who is thus told is a poor man, although the gift pledged is a large one, going back up on the pledge constitutes a great evil, for a vow has been made and he transgresses [this verse]: "He shall not break his word." Similarly, one who preens himself in public on the gift he will give to another, since he has accorded himself praise for his magnanimity, it is not right that he go back on his word once he has appropriated honor and praise through it.