What is the voice of zummat and the role of rikābukum?

ʿAntarah ibn Shaddād: Ruins, Love for ʿAblah and Tribal Conflict (verses 1–11)

• Passive past; rikāb is the passive subject
• Imperative; rikāb an absolute object
• Active imperfect; rikāb a preposition
• Active participle; rikāb an apposition