John Gill's Exposition of the Whole Bible
Numbers 5:12
Speak unto the children of Israel, and say unto them,.... It being an affair which concerned them:
if any man's wife go aside, and commit a trespass against him; the sin of adultery, which is a going aside out of the way of virtue and chastity, and a trespass against an husband, a breach of the marriage covenant with him, a defiling his bed, doing an injury and dishonour to him, bringing confusion into his family, and a spurious offspring to possess his substance: though this is to be understood, not of certain adultery, of which there is plain and full proof, for then there would be no occasion of such a trial, as is afterwards directed to; besides, her husband, in such a case, might put her away, and even, according to the law, she was to be put to death, Leviticus 20:10; but of her having committed it in the opinion of her husband, he having some ground of suspicion, though he could not be certain of it; and therefore, by this law, was allowed to make trial, that he might find it out, it at present only a suspected case, and a doubtful one; and the Jews k say,
"they never gave the waters drink but in a doubtful case:''
and so this may interpreted of her declining and departing from her husband's house, not keeping at home to mind the affairs of her family, but gadding abroad, and keeping company with another man, or other men; and that after she had been warned and charged by her husband to the contrary, and so had disobeyed him, and acted contrary to his will; and in that sense had committed a trespass, and so had given him suspicion of her unchastity, for which he might have some reason; if, as it is said in the Misnah l, he gave her an admonition before two witnesses, saying, have no talk with such a man, and yet she talks with him; or, as the commentators add m, be not secretly or in private with such an one, and yet goes into a private place with him, and stays so long with him that she may be defiled; this with them rendered her suspected.
k Bemidbar Rabba, sect. 9. fol. 195. 2. l Sotah, c. 1. sect. 1, 2. m Maimon. Bartenora in Misn. Bava Kama, c. 9. sect. 11.