Numbers 5:15 - Matthew Poole's English Annotations on the Holy Bible

Then, she persisting in her denial, and her husband requiring her submission to this way of trial. Her offering was partly because none were to appear before God empty, Exodus 23:15; partly, by way of solemn appeal to God, whom hereby she desired to judge between her and her husband; and partly, by way of atonement to appease God, who had for her sins stirred up her husband against her, and sent an evil spirit between them. See 1 Samuel 26:19. No oil nor frankincense, both because it was a kind of sin-offering, from which these were excluded, Leviticus 5:11, and to testify, her sorrowful sense of the hand of God, and of her husband's displeasure, and because she came thither as a delinquent, or one suspected of delinquency, and under an ill fame, and unpleasing both to God and men; as one that wanted that grace and amiableness and joy which oil signified, and that acceptance with God which frankincense designed, Psalms 141:2. Bringing iniquity to remembrance; both to God, before whom she appeared as a sinner, and to her own conscience, if she were guilty, and, if she were not guilty of this, yet it reminded her of her other sins, for which this might be a punishment.