Jamieson, Fausset and Brown on Numbers 30:1

CHAPTER 30

Nu 30:1-16. Vows Are Not to Be Broken.

1. This is the thing which the Lord hath commanded--The subject of this chapter relates to vowing, which seems to have been an ancient usage, allowed by the law to remain, and by which some people declared their intention of offering some gift on the altar or abstaining from particular articles of meat or drink, of observing a private fast, or doing something to the honor or in the service of God, over and above what was authoritatively required. In Nu 29:39, mention was made of "vows and freewill offerings," and it is probable, from the explanatory nature of the rules laid down in this chapter, that these were given for the removal of doubts and difficulties which conscientious persons had felt about their obligation to perform their vows in certain circumstances that had arisen.