דברי הימים א ד:כב פירוש: רש״י

And Jokim and the people of Kozeba until “and Jashubi Lehem.” All these were the sons of Shelah the son of Judah.

and Joash and Saraph Our Sages say that these were Mahlon and Chilion.

and the matters are ancient The meaning is: Do not say that since I began to trace the lineage of the people of our generation that they all came afterwards. All the people mentioned in this verse (were ancient) were early, [i.e.], they lived in earlier days.