Schaff's Bible Dictionary
PREACH'ING. The word is not used in the Bible in its present technical sense, but means proclamation by public authority, as a herald or crier. But ere the Bible closed the institution of preaching sprang up. and hence in the Epistles the Greek word approximates to our meaning. In the ancient Hebrew state there was no preaching, but after the Exile some instruction in the Law was given to the people, Neh 8, and our Lord improved the opportunities afforded him by the synagogue discourses to set forth the kingdom. See Synagogue.
Since the full establishment of the Christian Church preaching has been regarded as a sacred profession, and has, for the most part, been confined to an appointed and specially trained order of men.