Genesis 38:11
Then said Judah to Tamar his daughter in law, Remain a widow at thy father’s house, till Shelah my son be grown: for he said, Lest peradventure he die also, as his brethren did. And Tamar went and dwelt in her father’s house. Then said Judah to Tamar his daughter in law, Remain a widow at thy father’s house, till Shelah my son be grown: for he said, Lest peradventure he die also, as his brethren did. And Tamar went and dwelt in her father’s house.
Genesis 38:11 stands between the selling of Joseph into Egypt and his being bought by Potiphar, an officer of Pharaoh. It belongs to the account of the sin of Judah and of his family. That account is among the sad fruits of Jacob's having more than one wife, which included partiality, jealousy, envy, low moral standards, and crime.
The verse records Judah's instruction that Tamar remain a widow at her father's house until Shelah was grown. Judah gave this direction because he feared Shelah would die also, as his brethren had died. The chapter exposes sin so that it may be shunned rather than excused. It at the same time reveals God's remedy in love, mercy, and power.
Judah's direction for Tamar to remain a widow until Shelah was grown is an instance of the law of levirate marriage already recognized in patriarchal times. The law existed in germ and in special form before Moses and afterward became part of the Mosaic code. The so-called Mosaic laws therefore did not all originate with Moses. The chapter shows that Pharez, an ancestor of Christ according to the flesh, was born of Tamar, described as a harlot, who acted as a harlot with her father-in-law, placing a morally compromised family history within Christ's human ancestry.
The sinfulness of the human line from which Christ sprang tended to concentrate in Him all the weaknesses and sinful tendencies of fallen humanity. The flesh He assumed was therefore subject to the infirmities of the flesh and to death. This was a necessary part of the plan of redemption so He might suffer death and be able to sympathize with and succor tempted man. The presence of Tamar among Christ's ancestors shows His lineage included people with shameful histories, offering hope to the fallen.