4:12 be like . . . Perez. In a much earlier time, Judah had become the father of Perez because Onan refused to carry out his obligation as a close relative (Gen. 38:29). Perez became a symbol of the fruitful offspring. Now in the same way Boaz becomes the father of Obed (v. 21) because another person refused to carry out the levirate obligation. Despite human failures, the messianic line was preserved (Matt. 1:3, 5, 16).