A.T. Robertson Commentary Hebrews 8:11

"And they shall not teach every man his fellow-citizen, And every man his brother, saying, Know the Lord: For all shall know me, From the least to the greatest of them." — Hebrews 8:11 (ASV)

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 Lu 15:15; 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. 2:13, εσομα πεποιθως).