Ezra the priest is a great model of an expositor. Read with me Ezra 7:1-10:
Now after this, in the reign of Artaxerxes king of Persia, Ezra the son of Seraiah, son of Azariah, son of Hilkiah,  son of Shallum, son of Zadok, son of Ahitub,  son of Amariah, son of Azariah, son of Meraioth,  son of Zerahiah, son of Uzzi, son of Bukki,  son of Abishua, son of Phinehas, son of Eleazar, son of Aaron the chief priest—  this Ezra went up from Babylonia. He was a scribe skilled in the Law of Moses that the LORD the God of Israel had given, and the king granted him all that he asked, for the hand of the LORD his God was on him.
 And there went up also to Jerusalem, in the seventh year of Artaxerxes the king, some of the people of Israel, and some of the priests and Levites, the singers and gatekeepers, and the temple servants.  And he came to Jerusalem in the fifth month, which was in the seventh year of the king.  For on the first day of the first month he began to go up from Babylonia, and on the first day of the fifth month he came to Jerusalem, for the good hand of his God was on him.  For Ezra had set his heart to study the Law of the LORD, and to do it and to teach his statutes and rules in Israel.
Listen to what John Gill has to say about Ezra as he reflects on Ezra 7:10:
To attain to the knowledge of it, that he might be master of it, and expert in it, and know what was not to be done, and what to be done; he had set his heart upon this, bent his studies this way, and taken a great deal of pains in searching into it, in reading of it, and meditation on it; and to do it; he was not only concerned to get the theory of it, but to put it in practice, to exercise himself in it, that it might be habitual to him; and the rather, as his view and intentions were not merely for the sake of himself, but to teach in Israel statutes and judgments; and therefore it was not only necessary that he should have a large and competent knowledge of the laws, moral, ceremonial, and civil, but that he should act according to them himself, that so by his example, as well as by his instructions, he might teach the people (1 Chronicles through Psalm 72 pp. 117-118).
What an excellent model for an expositor — not just to study it, but also to live it, and not just to live it, but to teach it.