A Portion in Olam Haba According to One's Speech:

The pasuk states (Bereishis 2:16): "And Hashem commanded the man, to say..." Sefer Arvei Nachal (Parshas Bereishis) writes: "This indicates that the nature of a living person is to speak, to keep his mouth unsealed, as Chazal say (Chulin 89A): 'What is the 'umnus' (craft) of a man in this world? To makes himself like a mute. It is a hard job to be silent. For this reason, Hashem gave us the Torah, which is very deep. One must toil in it constantly. Thus, one can speak words of today at all times. (A non-Jew has no choice other than to speak about nonsense, as he has nothing else to discuss, but a Jew has the option to speak about Torah.) A man's main acquisition (portion in ths world) is dependent on his speech because a part of his soul leaves him with every word. When one speaks frivolous words, these words go to the impure forces, but when one speaks words of Torah and holiness, the words – which are a portion of his neshama – go to the source of holiness." He adds: "If one wants to determine if he has a share in Olam Haba or not, he should contemplate what he spoke about throughout his life. If he was careful not to speak wasteful, pointless words, and all his words were used for Torah and holy matters besides for a few used for mundane things when necessary, he will know that his soul is holy and he has a portion in Olam Haba. But if he always spoke about nonsense, he will know that even if he did many mitzvos and good deeds, it won't help him because his soul is in the grasp of impure forces."