Deuteronomy 17:9 - Joseph Benson’s Commentary on the Old and New Testaments

Unto the priests That is, unto the great council, which consisted chiefly of the priests and Levites, as being the best expositors of the laws of God, by which all those controversies were to be decided. And the high-priest was commonly one of that number, comprehended here under the priests, whereof he was the chief. By judges, here, seems to be meant those supreme judges of the nation, whom God raised up when the Israelites were oppressed by their enemies, such as Gideon, Jephthah, Samson, Samuel, &c. Such judges were, by their office, invested with the highest authority, civil as well as military; for to judge Israel was to administer justice, as well as to command armies. Moses seems to intimate, that the Hebrew commonwealth was to retain, after his death, the same form as it had now when he was alive; for he himself was the supreme judge, or administrator of justice, to whom the more difficult causes were to be referred, Deuteronomy 1:17. So Joshua was judge after him, and many other.