DEUT1300 As Maimonides explains, "By this injunction, we are commanded to fulfill every obligation that we have taken upon ourselves by word of mouth" (Book of the Commandments, Positive Commandment #94). Although this verse seems to be speaking of someone who has made a formal vow to do something, subsequent Jewish law regards it as obligatory to fulfill whatever you have said you were going to do. Therefore, keep your word, particularly if someone is relying on it, and evening when it is inconvenient to do so. Not infrequently, we offer to do someone a favor. At the time we commit ourselves, we really intend to do it. Later, however, we realize that the favor is more inconvenient or time-consuming than we originally thought, and we are tempted not to follow through. Nonetheless, we remain obligated to carry out our word (see Rabbi Jonah Gerondi, The Gates of Repentance 3:183). Rabbi Avrohom Ehrman notes that the responsibility to keep our word increases in proportion to the degree upon which it is relied. Thus he rules that if we tell someone, "I will take you to the airport" (a long drive), and a difficulty arises, "The speaker may back down from his word. However, if the passenger says, for example, 'I'm relying on you,' and the speaker responds, 'Yes, you can rely on me,' that is considered a promise, because the passenger [fully] expects the speaker to keep his word." (Ehrman, Journey to Virtue, 93). One advantage of this is that you will be more cautious before promising to do something. Some people casually offer to do favors in order to be well thought of, but don't follow through, and incur far greater animosity than they would have done if they had not made the offer in the first place. Rabbi Aaron Levine summarizes this aspect of the Jewish tradition on truthtelling: "One should never make a commitment unless one fully intends to carry it out." (Levine, Case Studies in Jewish Business Ethics, 27).