This will result in what Yahweh himself declares: “And you shall know that I am Yahweh your God, dwelling on Zion, my holy Mountain, and Jerusalem shall be holy” (Joel 4:17, ET 3:17). The holiness of Jerusalem does have ethical implications for God’s people, for as Barton notes, “Knowing the secret of the future that God is about to implement can challenge the hearers to radical obedience, in preparation for taking part in the glories of the age to come.”  For this future to be realized, however, God’s people must know him in his justice and his mercy, and Joel proclaims that they will know that he is Yahweh when he saves them through judgment for his own glory, acquitting them of guilt and dwelling in Zion (4:21, ET 3:21).

James M. Hamilton, Jr.
God’s Glory in Salvation Through Judgment, p. 241