And they shall teach no more every man his neighbour, and every man his brother, saying, Know the LORD: for they shall all know me, from the least of them unto the greatest of them, saith the LORD: for I will forgive their iniquity, and I will remember their sin no more.
They won't need to teach others about knowing the Lord anymore because everyone, from the smallest to the greatest, will personally know Him. The Lord promises to forgive their wrongdoings and won't remember their sins anymore.