Saying, master,.... Rabbi, or doctor, as he was usually called;Moses said, in De 25:5if a man die having no children, his brother shall marry his wife, and raise up seed unto his brother; which, though not expressed in the self same words, yet is the sense of the passage referred to, and was a practice in use before the times of Moses, as appears from the case of Er and Onan; the design of which was, to preserve families, and keep their inheritances distinct and entire.
This law only took place, when a man died without children; for if he left any children, there was no need for his brother to marry his wife; yea, as a Jewish writer observes , she was forbidden, it was not lawful for him to marry her, and was the case if he had children of either sex, or even grandchildren: for as another of their commentators notes , his having no child, regards a son or a daughter, or a son's son, or a daughter's son, or a daughter's daughter; and it was the eldest of the brethren, or he that was next in years to the deceased, that was obliged by this law , though not if he had a wife of his own; and accordingly in the following case proposed, each of the brethren married the eldest brother's wife in their turn, according to the course of seniority; and by this law, the first child that was born after such marriage, was reckoned the seed of the deceased, and was heir to his inheritance.
The Jews in their Misna, or oral law, have a whole tract on this subject, called Yebamot, which contains various rules and directions, for the right observance of this law. Aben Ezra in Deut. xxv. 5.
Jarchi in ib. Vid. Maimon. Hilch. Yebum, c. 1. sect. 3. Jarchi in Deut. xxv. 5. Misn. Yebamot, c. 2. sect. 8. & 4, 5. Maimon. Hilch. Yebum, c. 2. sect.