Why Vows Outweigh Oaths and the Danger of Breaking Them

"And Moses spoke to the heads of the tribes, etc., If a man vows a vow to the LORD" (Numbers 30:2-3). Let our master teach us: how do konamot (vows of abstinence) and vows work? Thus have our masters taught: [If one says] "Konam that I shall not sleep, that I shall not speak, that I shall not walk"; one who says to his wife "Konam that I shall not have relations with you" — such a one falls under "He shall not break his word." [If one swears an oath] "that I shall not sleep," "Konam that I shall not speak, that I shall not walk" — it is forbidden. There is a stringency in oaths beyond vows, and in vows beyond oaths. How so? [If one says] "Konam that I shall not make a sukkah," "a lulav that I shall not take up," "tefillin that I shall not put on" — with vows it is forbidden to put them on or to make them, even though they are commandments; but with oaths it is permitted, because one does not swear to transgress the commandments. The Holy One, blessed be He, said to Israel: Be careful with vows, and do not be lax with them, for whoever is lax with vows ends by being faithless with oaths, and one who is faithless with oaths denies Me, and he has no pardon forever, as it is said, "For the LORD will not hold guiltless, etc." (Exodus 20:7). And another verse says, "And you shall swear, 'As the LORD lives,' etc." (Jeremiah 4:2). The Holy One, blessed be He, said to Israel: Do not suppose that you are permitted to swear by My name even in truth; you are not allowed to swear by My name unless all these qualities are in you: "The LORD your God you shall fear, [and Him you shall serve, and to Him you shall cleave, and by His name you shall swear]" (Deuteronomy 10:20).