This is a passage that I have been coming back to over and over during the past year. (I first heard it referenced in a sermon at our church.) It speaks primarily to kingship and mentions the issue of judging rightly (pursuit of the good), allowing me to categorize it under that heading, although it touches all three. (More on this theme tomorrow from Maximus the Confessor, as I populate these first several days with old treasures.)
To reign with Christ means to experience in one’s own life the restoration of the royal office. By virtue of creation man held the threefold office of prophet, priest, and king. As prophet his mind was illumined so that he knew God. As priest his heart delighted in God. As king his will was in harmony with God’s will. This threefold office, lost through the fall, is restored by God’s grace. The joyful response of the believer’s will to the will of Christ, that response which is true freedom, is the basic element in this reigning with Christ. Moreover, even during the period before death Christians rule the world by means of their prayers, in the sense that again and again judgments occur in answer to prayer (Rev. 8:3–5). In heaven they are even closer to the throne than are the angels (Rev. 4:4; 5:11). In fact, they sit with Christ on his throne (Rev. 3:21), sharing his royal glory. And when Christ returns, the saints sit and judge with him (Ps. 149:5–9; I Cor. 6:2, 3).
From New Testament Commentary: Exposition of the Pastoral Epistles. Vol. 4. by W. Hendriksen and S.J. Kistemaker (Grand Rapids: Baker Book House, 1979. 258–259.