If a man makes a vow to the LORD or swears an oath to obligate himself by a pledge, he must not break his word; he must do everything he has promised.
KJV
If a man vow a vow unto the LORD, or swear an oath to bind his soul with a bond; he shall not break his word, he shall do according to all that proceedeth out of his mouth.
ASV
When a man voweth a vow unto Jehovah, or sweareth an oath to bind his soul with a bond, he shall not break his word; he shall do according to all that proceedeth out of his mouth.