Will do his will (θέλῃ τὸ θέλημα αὐτοῦ ποιεῖν)
This is a notable illustration of the frequent blunder of the A.V. in rendering θέλειν, to will or determine, as a mere auxiliary verb. By overlooking the distinct meaning of the verb to will, and resolving willeth to do into will do, it sacrifices the real force of the passage. Jesus says, if it be one's will to do; if his moral purpose is in sympathy with the divine will.
He shall know
Sympathy with the will of God is a condition of understanding it.
Of God (ἐκ τοῦ Θεοῦ)
Better, from; proceeding out of.
Of myself (ἀπ' ἐμαυτοῦ)
Of myself is misleading, being commonly understood to mean concerning myself. Rev., correctly, from myself; without union with the Father. Compare Joh 5:30.