Er
Er is the name of three different men in Scripture: the firstborn son of Judah whom Yahweh struck down for wickedness, a later descendant of Judah through Shelah, and an unrelated ancestor in the genealogy of Jesus. Most of the textual weight falls on the first.
Er, Judah's Firstborn
Er is born to Judah by the daughter of Shua, a Canaanite woman, after Judah turns aside to the Adullamite Hirah (Gen 38:1). The birth notice is brief: "And she became pregnant, and gave birth to a son; and he named him Er" (Gen 38:3). His brothers Onan and Shelah follow (Gen 38:4-5).
Judah arranges his marriage: "And Judah took a wife for Er his firstborn, and her name was Tamar" (Gen 38:6). The marriage produces no children, and the reason is given without elaboration: "And Er, Judah's firstborn, was wicked in the sight of Yahweh. And [the Speech of] Yahweh slew him" (Gen 38:7). The text does not specify the wickedness; it only records the verdict and the act.
Er's death triggers the levirate sequence with Onan and, eventually, the encounter between Judah and Tamar that produces Perez and Zerah. The Chronicler later restates the indictment in summary form: "And Er, Judah's firstborn, was wicked in the sight of Yahweh; and he slew him" (1Ch 2:3).
Genealogical Memory
Subsequent rosters carry Er forward as a name even though his line ended with him. The migration list to Egypt records him among Judah's sons but immediately notes his death: "And the sons of Judah: Er, and Onan, and Shelah, and Perez, and Zerah; but Er and Onan died in the land of Canaan" (Gen 46:12). The wilderness census repeats the same paired notice: "The sons of Judah: Er and Onan; and Er and Onan died in the land of Canaan" (Nu 26:19). In the tribal arithmetic of Israel, Er is present as a name and absent as a line.
A Second Er, Son of Shelah
Judah's surviving son Shelah later has a descendant who also bears the name. The Chronicler lists him among Shelah's sons: "The sons of Shelah the son of Judah: Er the father of Lecah, and Laadah the father of Mareshah, and the families of the house of those who wrought fine linen, of the house of Ashbea" (1Ch 4:21). This Er is a clan father in Judah, distinct from his slain great-uncle.
A Third Er in the Genealogy of Jesus
Luke's genealogy of Jesus names a third, otherwise unknown Er: "the [son] of Melchi, the [son] of Addi, the [son] of Cosam, the [son] of Elmadam, the [son] of Er" (Lu 3:28). He is a link in the chain between Joseph and David, with no narrative attached.