Do not break oaths or vows

"If a man makes a vow to the LORD, or takes an oath to bind himself with a binding obligation, he shall not violate his word; he shall do according to all that proceeds out of his mouth.

Hebrew

ג אִישׁ כִּי-יִדֹּר נֶדֶר לַיהוָה, אוֹ-הִשָּׁבַע שְׁבֻעָה לֶאְסֹר אִסָּר עַל-נַפְשׁוֹ--לֹא יַחֵל, דְּבָרוֹ: כְּכָל-הַיֹּצֵא מִפִּיו, יַעֲשֶׂה.

Greek

(30:3) ἄνθρωπος ἄνθρωπος, ὃς ἂν εὔξηται εὐχὴν κυρίῳ ἢ ὀμόσῃ ὅρκον ἢ ὁρίσηται ὁρισμῷ περὶ τῆς ψυχῆς αὐτοῦ, οὐ βεβηλώσει τὸ ῥῆμα αὐτοῦ· πάντα, ὅσα ἐὰν ἐξέλθῃ ἐκ τοῦ στόματος αὐτοῦ, ποιήσει.

• Parashah: Mattot
• Sefer HaChinuch: 407
• Mishneh Torah: Promises — Vows

• Numbers 30:2

Enumeration and classification from BibleData. The Greek is the Septuagint reading of the same verse, carried by the source for comparison.