KJV : That which is gone out <04161> of thy lips <08193> thou shalt keep <08104> (8799) and perform <06213> (8804); [even] a freewill offering <05071>, according as thou hast vowed <05087> (8804) unto the LORD <03068> thy God <0430>, which thou hast promised <01696> (8765) with thy mouth <06310>.

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NASB : "You shall be careful to perform what goes out from your lips, just as you have voluntarily vowed to the LORD your God, what you have promised.

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NASB# : "You shall be careful<8104> to perform<6213> what<4161> goes<4161> out from your lips<8193>, just<3512> as you have voluntarily<5071> vowed<5087> to the LORD<3068> your God<430>, what<834> you have promised<1696>.