Today's Daily Halacha was orated by guest speaker, HaGaon HaRav Yaakov Hillel
The Torah (Bamidbar 30:3) teaches, regarding the mitzvah to fulfill ones oaths, "he must not profane his words; he shall do whatever came out of his mouth." The simply understanding is that whatever he says he should not treat lightly, like hulin (lo yahel devaro), but rather he should fulfill.
The Rabbis, however, explain this verse in a more profound way.
The verse begins, "lo yahel devaro" (he must not profane his words) - a person should always protect his tongue; he should not speak lashon hara or rehilut. Rather, he should guard his tongue. The mouth is one of the most fantastic of Gods creations. There are five sounds which emanate from the different parts of the mouth, and every word is made up of letters which are created from these different parts - the lips, the teeth, the tongue, the throat, and the cheeks. Without thinking we are able to use all of these parts of the mouth in order to create the sounds of our words and sentences. The power of speech is great- and a person should only use speech for the purpose for which is was created.
The Rabbis teach that one who protects and guards his tongue, fulfilling the first part of the verse, will also merit to fulfill the second part of the verse. The verse continues, "kechol hayetze mipiv yaaseh" (he shall do whatever came out of his mouth) - one who is careful with his words, his words will come true.
This is one of the reasons why people turn to great hachamim for advice, guidance and blessings- the words of those who guard their mouths are very powerful.
