| Clarke's Commentary on the Bible Betrothed her unto his son, he shall deal with her - He shall give her the same dowry he would give to one of his own daughters. From these laws we learn, that if a man's son married his servant, by his father's consent, the father was obliged to treat her in every respect as a daughter; and if the son married another woman, as it appears he might do, Exodus 21:10, he was obliged to make no abatement in the privileges of the first wife, either in her food, raiment, or duty of marriage. The word ענתה onathah, here, is the same with St. Paul's οφειλομενην ευνοιαν, the marriage debt, and with the ὁμιλιαν of the Septuagint, which signifies the cohabitation of man and wife.
Gill's Exposition of the Entire BibleAnd if he have betrothed her unto his son,.... Not caring to betroth and marry her himself, as being more suitable in age for his son than for himself: he shall deal with her after the manner of daughters; as if she was his daughter, and give her a dowry: or the son shall treat her after the manner the daughters of Israel are treated when married, by giving her food, raiment, and the duty of marriage, so Jarchi: or after the manner of the daughters of Israel that are virgins, and who are not sold, as Aben Ezra.
Geneva Study BibleAnd if he have betrothed her unto his son, he shall deal with her {h} after the manner of daughters. (h) That is, he shall give his dowry.
Wesley's Notes 21:9 After the manner of daughters - He shall give her a portion, as to a daughter.
Matthew Henry's Concise Commentary21:1-11 The laws in this chapter relate to the fifth and sixth commandments; and though they differ from our times and customs, nor are they binding on us, yet they explain the moral law, and the rules of natural justice. The servant, in the state of servitude, was an emblem of that state of bondage to sin, Satan, and the law, which man is brought into by robbing God of his glory, by the transgression of his precepts. Likewise in being made free, he was an emblem of that liberty wherewith Christ, the Son of God, makes free from bondage his people, who are free indeed; and made so freely, without money and without price, of free grace. | 
