“The sons of Shelah son of Judah were Er the father of Lecah, Laadah the father of Mareshah, and the families of the house of linen workers at Beth-ashbea. Jokim was with the men of Cozeba, Joash, and Saraph, who married into Moab, but returned to Lehem. The records are ancient. These were the potters and inhabitants of Netaim and Gederah. They lived there with the king for his work.”
Shelah was the 3rd or youngest son of Judah as outlined in Genesis 38, before the episode with Tamar. However, at the beginning of this chapter he was not listed as a son of Judah. Er was the name of his brother in the Genesis story so it does not seem strange that he should name his son after his brother, who had died. This, however, is the only mention of Lecah or Laadah. Mareshah is definitely a town in Judah and may have been a person. This is the only mention of the linen workers of Beth-ashbea. Linen was a big deal for the holy of holies. This is the only mention of Jokim, Cozeba, and Saraph. Joash was of course the name of the king of Judah (835-796 BCE) and the name of the king of Israel (798-783 BCE). There were over 8 people in the biblical literature with this name. This is the only mention of Lehem, but it might refer to Bethlehem. Somehow this Saraph went to Moab and then returned to Lehem. The biblical author claims that this is based on a very old document, but does not say what it is. Apparently these people were the potters or artisans living in Netaim and Gederah. These towns might be near Gezer, in Judah since their names only appear here, but there is no definite identification. The king might have had access to them in these towns.