In Jewish tradition the third commandment "LO TISA" refers to the prohibition of swearing in the name of God in vain or unnecessarily (shebu'at shav). Following Maimonides, it also extends to the prohibition of reciting a blessing in vain. Why? Ashebu'a is basically a statement, an affirmation of a belief or a fact. In a blessing we are also making a statement. We assert an idea or a belief about God, while pronouncing His name. For example, when I say the blessing "bore feri ha'ets" I'm not saying "Thank You God for this fruit" but literally: "Blessed are You, HASHEM our God, King of the universe, who is the Creator of the fruit of the tree". In other words: I'm stating and acknowledging that You -HASHEM- are the Creator of this fruit. Therefore, if I pronounce this or a similar statement unnecessarily I would be transgressing the third commandment. This is the source of the halakhic principle: "safeq berakhot lehaqel". Which indicates that in a situation where I'm not sure if I should or should not say a berakha I should abstain, lest I recite an unnecessary berakha (lebatala) and transgress LO TISA.
The former Chief rabbi of Israel , Rabbi Shelomo 'Amar, explains that this commandment also extends to a different area. The words LO TISA which are commonly translated as "You shall not take..." literally mean: "You shall not 'carry' the name of God in vain". He sees LO TISA also as a warning against showing-off religiosity or piety. Rabbi 'Amar denounces the unfortunate practice of some people who would disguise themselves as pious, adopting publicly extra restrictions, performing eccentric movements while praying, or carrying out religious acts in unusual ways with the intention of impressing people and making them believe that he is a pious Jew. This behavior will be an example of "carrying God's name in vain". Pretending that one does something with God in mind when in reality is doing it for his or her own interest.
Rabbi 'Amar explains that contrary to those who display religious zeal in public to impress others, a real pious Jew is first of all humble, and his piety is observed privately and discreetly.
