They shall not teach (ου μη διδαξωσιν). Strong double negative (ου μη) with the first aorist active (futuristic) subjunctive of διδασκω.

His fellow-citizen (τον πολιτην αυτου). See Luke 15:15; Luke 19:14.

Know the Lord (Γνωθ τον κυριον). Second aorist active imperative of γινωσκω. In the new covenant all will be taught of God (Isaiah 54:13; John 6:45), whereas under the old only the educated scribe could understand the minutiae of the law (Dods). See Paul's comparison in 2. Corinthians 3:7-18.

Shall know (ειδησουσιν). Future perfect active, old form of οιδα (note γινωσκω just before of recognizing God), one of the rare future perfects (cf. Hebrews 2:13, εσομα πεποιθως).