קבלה על במדבר 30:3

How much more so will he who fears the Lord (Exod. 9:20) give more love, awe, fear, and humility, will he worry because of his sins, and will he be concerned lest he increase his sins with the iniquity of erring in the statements [concerning] the knowledge of the holy God (Josh. 24:19) lest his soul offer itself in restitution (Isa. 53:10). His only recourse (Esther 4:11) and the territory of his inheritance (Deut. 32:9) is to strip himself, and to cut and offer [himself] as a complete sin offering. He will be morally strong to bind with a bond forbidding (Num. 30:3) that which he has not heard from his teachers. He makes even all his paths (Prov. 5:21) and the utterances of his lips (Ps. 21:3). For if he falls (Deut. 22:8), who will raise him up? (Gen. 49:9). The Lord alone will lead him, and there is no strange god with him (Deut. 31:12) who has apportioned to test in them and afflicted [them] because of their iniquities (Ps. 107.17).

The reason is because the Torah says “He shall do according to all that proceeds out of his mouth” (Numbers 30:3), since the speech that is spiritual is similar to the sperm that is physical. Just like from the lower Brit one must not emit semen in vain, but only into a female, so too one must not say words in vain except for the sake of bringing oneself to a place of action, which is the female, and thus he unites the Brit of the tongue with the female. If he does not fulfill it, Chas Veshalom, then it is like he emitted semen in vain, which is the voice and speech that comes out of the Brit of the tongue, and therefore he will also damage the Brit with semen in vain, since a transgression leads to a transgression.