For not he that commendeth himself is approved, but whom the Lord commendeth.
Is approved - stands the test of the final trial х Dokimos (G1384)]: a metaphor from testing metals (Romans 16:10; 1 Corinthians 11:19). On the other hand, those finally rejected by the Lord are termed 'reprobate silver" (Jeremiah 6:30).
Whom the Lord commendeth - to whom the Lord has given, as His "letter of commendation," the believers whom he was instrumental in converting; as was Paul's case (2 Corinthians 3:1-3).