'Voluntarily' in the Bible

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.

It shall come about, when their fathers or their brothers come to complain to us, that we shall say to them, ‘Give them to us voluntarily, because we did not take for each man of Benjamin a wife in battle, nor did you give them to them, else you would now be guilty.’”