In the Hebrew Scriptures, the word cham designates the husband’s father (Ge 38:13, 25; 1Sa 4:19, 21), and its feminine form, cha·mohthʹ, the husband’s mother (the wife’s mother-in-law).—Ru 1:14; Mic 7:6.
The Hebrew verb cha·thanʹ means “form a marriage alliance.” (De 7:3; 1Sa 18:20-27; 1Ki 3:1; 2Ch 18:1) The father-in-law on the bride’s side, the wife’s father, is designated by a masculine participial form of cha·thanʹ. Its feminine participial form refers to mother-in-law.—De 27:23.
Because an engaged couple were considered as bound although the couple had not yet come together in marriage, the woman was spoken of as the man’s wife. (Jg 14:20) Therefore, the man was called “son-in-law” (a noun drawn from cha·thanʹ being used) regardless of whether the marriage alliance had been fully consummated (Jg 19:5; 1Sa 22:14; Ne 6:18; 13:28) or was only contemplated, as in the case of Lot’s “sons-in-law.” (Ge 19:12, 14; compare Jg 15:6.) Lot’s daughters were only betrothed; otherwise they would most likely have been with their husbands and not living in their father’s house. That the two men were only prospective, not actual, sons-in-law (engaged to Lot’s daughters but not as yet married to them) is indicated by the Hebrew, which allows for the rendering: “[Lot’s] sons-in-law who were to take [or, were intending to take] his daughters.”—Ge 19:14, NW; Ro; compare JB; Mo; RS.
In the Christian Greek Scriptures, pen·the·rosʹ is translated “father-in-law” (Joh 18:13); the feminine form, pen·the·raʹ, is rendered “mother-in-law.”—Mt 8:14; 10:35; Mr 1:30; Lu 4:38; 12:53; see DAUGHTER-IN-LAW.