Better not to vow than to vow and not fulfill/ better is it that you should not vow than that you should vow and not pay
It is better not to make a promise than to make a promise and not keep it (a vow is a vow made out of thin air)
("Better not to vow than to vow and not fulfill" — Ecclesiastes 5:4)
Translation
Expression (Hebrew)
טוֹב אֲשֶׁר לֹא תִדּוֹר מִשֶּׁתִּדּוֹר וְלֹא תְשַׁלֵּם
Definition (Hebrew)
עָדִיף שֶׁלֹּא תַּבְטִיחַ הַבְטָחוֹת מֵאֲשֶׁר תַּבְטִיחַ וְלֹא תְּקַיֵּם (תִדּוֹר מִלְּשׁוֹן לִנְדֹּר נֶדֶר)
("טוֹב אֲשֶׁר לֹא תִדֹּר מִשֶּׁתִּדּוֹר וְלֹא תְשַׁלֵּם"- קֹהֶלֶת ה ד)