And Judah said unto Onan, Go in unto thy brother's wife, and marry her, and raise up seed to thy brother.
Marry her, and raise up seed to thy brother. The first instance of a custom which was afterward incorporated among the laws of Moses, that when a hushand died leaving a widow, his brother next of age was to marry her, and the issue, if any, was to be served heir to the deceased (cf. Deuteronomy 25:5). The time and circumstances in which this practice originated are not known. It seems to have been early introduced, and arose out of the great importance attached to the primogeniture.