This week's parsha commences with Hashem describing to Moshe the relationship that He had with the Avos. "I appeared to Avraham, Yitzchak and Yaakov as Keil Shakai, but with My Name Ado-nai I did not make Myself known to them" (Shemos 6:3). Rashi explains that the name "Ado-nai" connotes Hashem's attribute of truth i.e. being true to His word. Hashem promised numerous things to the Avos, but they were only to come to fruition in the future. The fulfillment of His promises would be the manifestation of His attribute of truth indicated by the Name "Ado-nai."
When Yisro suggested to Moshe that he find men to assist in judging Bnei Yisrael, he added that the candidates should be "men of truth" (ibid. 18:21). Rav Wolbe (Shiurei Chumash) points out that, here too, Rashi explains that this appellation refers to men whose guarantee can be relied upon. Truth is not defined solely by not falsifying facts of the past; it pertains also to one's pledges regarding the future. There was no question that Hashem would fulfill His promises. Nevertheless, He felt that His name of truth had not been revealed because those promises were not fulfilled in the lifetime of the Avos. Likewise, even if a person has full intention of fulfilling his promises, unless he actually makes good on his word he cannot be considered a man of truth.
A similar idea can be found in the bracha of Kiddush Levana. Once a month we declare about the heavenly orbs, "A fixed time was given to them that they not change their instructions... doers of truth." Rashi (Sanhedrin 42a) explains that "doers of truth" refers to the fact that they never change their course. The world is not eternal, but as long as it does exist, it exists without change. It is possible to calculate the exact time, down to the second, that the moon will begin its monthly cycle in one thousand years from now. The truth of the sun and the moon is defined by their constancy and lack of deviation from their defined course. Chazal tell us (Shabbos 104a) that truth has stability and permanence since the letters of the word "emes" all stand firmly on their bases while the letters of "sheker" lack the same stability.
Indeed, the truth of a human being can also be determined by his constancy and lack of deviation from his pledges. A person faithful to his word is a man of truth, while not keep one's word indicates a serious flaw. The Gemara states (Bava Metzia 49a) that one who pays for an item (thereby committing to buy it) but has not yet taken possession with a kinyan, is halachically permitted to back out of his purchase. However, regarding such people it is said, "He Who brought retribution upon the Generation of the Flood and the Generation of Dispersion, will bring retribution upon one who does not stand by his word."
While most people refrain from outright lies, failing to fulfill one's promise is not perceived with the same severity. No politician could hope to be elected if his campaign was full of blatant falsehoods. Nevertheless, he might pledge more than he ever had intentions of fulfilling and often manage to win the election. He might not be a liar, but he is also not a man of truth! Yet, mussar dictates that we point a finger not at others, rather, at ourselves. We are to look in the mirror and determine if we conform to these criteria. Have we pledged on Yom Kippur to improve and failed to fulfill our word? Do we maintain a level of consistency with regard to Shacharis or do we bounce from minyan to minyan depending on the time we wake up? Reneging is always the easy way out. However, truth be told, it feels a lot better to be truthful and fulfill one's word thereby emulating the attribute of "Ado-nai!"