The sons of Judah; Er, and Onan, and Shelah: which three were born unto him of the daughter of Shua the Canaanitess. And Er, the firstborn of Judah, was evil in the sight of the Lord; and he slew him. (1 Chronicles 2:3)
The inclusion of this statement from the original record (see Gen. 38:7) is in keeping with the chronicler’s purpose of presenting an account that shows the terrible fruitage of sin and the rewards of righteousness.