Wormwood was a familiar plant in the middle east, proverbial for bitterness (Proverbs 5:4) and comparable to the taste of poison (Amos 6:12; Deuteronomy 29:18; Jeremiah 23:15). Turning justice into bitterness means perverting justice. Casting righteousness to the ground means ignoring and having no concern for righteousness.
Biblically righteousness and justice are often used together. These two Hebrew words are used as a summary of the covenantal responsibilities of God’s people. Just as justice (Isaiah 30:18) and righteousness (Micah 7:9) are essential activities of the LORD, they must become prime duties of his people, especially the leaders (Micah 6:8; Deuteronomy 6:24; Isaiah 1:21; Isaiah 5:7; Isaiah 28:17; Jeremiah 22:16–17; Psalm 72:1–4, Psalm 72:12–14; Proverbs 16:8; Proverbs 21:3). In terms of the words themselves, justice puts a slight emphasis on establishing and preserving order in society by righting wrongs and punishing wrong-doers. Righteousness emphasises the relationships that covenantal society entails and insists that each partner do all that is necessary to keep the covenant working right.
7 O you who turn justice to wormwood and cast down righteousness to the earth!