The Tora is very strict about our obligation to say the truth and our duty to keep away from falsehood. Speaking the truth and acting with truthfulness is seen in Judaism as one of the highest religious imperatives. So much so that our Rabbis asserted that upon our arrival to the World to Come (=the afterlife) we are faced with three questions, aimed to asses the spiritual level we have achieved in our worldly existence. The very first question we are asked by the heavenly court is about our financial behavior. nasata venatata bemuna? "Did you handle your money matters with integrity?" Clearly, the way we act in our businesses and material dealings is seen by our Tora as the most accurate indicator of our religious level.
Our rabbis explain that the seal of HaShem Almighty is "EMET" (=The Truth). The seal of a King, similar to today's signature, was the visual mark or the logo that identified the King. When people saw the seal in a letter, they knew that letter was coming from the King. Similarly, in this world the presence of haShem our God is represented by The Truth. In a sense, every time we act with truthfulness we turn into representatives of HaShem Almighty. By performing an act of integrity (and the higher the losses we are willing to take by upholding the truth, the greater the merit!) we become "HaShem's seal". Our actions will inspire people who see what we do to say: "This is coming from HaShem" (or, from His Tora).
On the contrary, if we lie, fabricate stories or act deceitfully, we move further away from Him. When a Jew (and especially, an observant Jew) acts deceitfully He is "misrepresenting" HaShem. He desecrate His name, as if he would have 'sold' God's reputationfor money...
Good news for those who know Hebrew. You can find now yalqut yosef, the book of Halakha of rabbi Obadia Yosef, online and free. Click here.