John Gill Bible Commentary

Then said Judah to Tamar his daughter in law,.... After the death of his two sons, who had successively married her: remain a widow at thy father's house till Shelah my son be grown: who was his third and youngest son, though perhaps not more than a year younger than Onan; but he might not choose he should marry so soon as his brethren had done, for a reason following: according to the custom and law of marrying a brother's wife, who died without issue, she in course was to be the wife of Shelah; since if there were ever so many brothers, they all married such an one in turn, until there was issue by one of them, see Mat 22:25; as Judah knew this, he pretended at least to give her to his son for wife, only would have it put off till he was at age of maturity, or was more grown; and therefore desires her to keep herself unmarried to any other person until that time; and advises her to go to her father's house, and continue there, which he did to prevent any intrigues between them, lest his son should be tempted to marry her sooner than it was his will, and she should solicit him to it: for he said; not to Tamar, but within himself: lest peradventure he die also as his brethren did; by which it seems, that he was ignorant of the true cause of their death, but thought it was either owing to their marrying too young, or to something in the woman unfortunate and unhappy; and he might not really intend he should marry her at all, only made use of an excuse for the present: and Tamar went and dwelt in her father's house; she had dwelt in Judah's house in the time of her two husbands, but now by his advice she removed to her own father's house; which very probably was in the same place, and her father yet living, who received her, and with whom she continued, see Lev 22:13.