In the Hebrew Scriptures, the word hham designates the husband’s father (Gen. 38:13, 25; 1 Sam. 4:19, 21), and its feminine form, hha·mohthʹ, the husband’s mother (the wife’s mother-in-law).—Ruth 1:14; Mic. 7:6.
The father-in-law on the bride’s side, the wife’s father, is designated by a masculine participial form of the Hebrew verb hha·thanʹ. Its feminine participial form refers to mother-in-law. (Deut. 27:23) Other forms of the word hha·thanʹ are also translated “marriage alliance.”—Deut. 7:3; 1 Sam. 18:20-27; 1 Ki. 3:1; 2 Chron. 18:1.
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. (Judg. 14:20) Therefore, the man was called “son-in-law” (a noun drawn from hha·thanʹ being used) regardless of whether the marriage alliance had been fully consummated (Judg. 19:5; 1 Sam. 22:14; Neh. 6:18; 13:28) or was only contemplated, as in the case of Lot’s “sons-in-law.” (Gen. 19:12, 14; compare Judges 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 his daughters.”—Gen. 19:14, NW; Mo; Ro; compare JB; RS.
In the Christian Greek Scriptures, pen·the·rosʹ is translated “father-in-law” (John 18:13); the feminine form, pen·the·raʹ, is rendered “mother-in-law.”—Matt. 8:14; 10:35; Mark 1:30; Luke 4:38; 12:53; see DAUGHTER-IN-LAW.