This means that he provides enough evidence for each person who hears him to decide whether he is right or wrong. See how "recommend ourselves" is translated in [2 Corinthians 4:2](../04/01.md).
You can make clear the understood information. Alternate translation: "the one whom the Lord recommends is the one of whom the Lord approves" (See: [[rc://en/ta/man/translate/figs-ellipsis]])