Albert Barnes Commentary 2 Chronicles 20:35

"And after this did Jehoshaphat king of Judah join himself with Ahaziah king of Israel; the same did very wickedly:" — 2 Chronicles 20:35 (ASV)

After this - Jehoshaphat’s history had been formally completed in 2 Chronicles 20:34. Consequently, we cannot place much emphasis on the timing indicated by the words “after this,” as they are detached from the context to which they originally referred. Regarding the history in 2 Chronicles 20:35–37, see the marginal references and notes.