An oath, i.e. a form of cursing or imprecatory oaths, that when they would curse a person, they may wish that they may be as cursed and miserable as thou wast upon this occasion. See the phrase Isaiah 65:15 Jeremiah 29:22 and compare Genesis 48:20 Ruth 4:11,12. Thy thigh; a modest signification of the genital parts, used both in Scripture, as Genesis 46:26 Exodus 1:5, and other authors, that the sin might be evident in the punishment. To rot, Heb. to fall, i.e. to die or waste away, as the word is used, 1 Chronicles 21:14, compared with 2 Samuel 24:15. To swell, suddenly and violently till it burst, which the Jews note was frequent in this and like cases, as Exodus 32:20. And it was a clear evidence of the truth of their religion.
Related Commentaries of Numbers 5:21
Numbers 5:21
21 Then the priest shall charge the woman with an oath of cursing, and the priest shall say unto the woman, The LORD make thee a curse and an oath among thy people, when the LORD doth make thy thigh to rot,b and thy belly to swell;