What is the key contrast in jarra ʿalayhim from the opening to the ending?

Zuhayr ibn Abī Sulmā: Ḥuṣayn ibn Ḍamḍam, Revenge and the Cost of Bloodshed (Verses 33–42)

• The opening asserts harm; the ending negates responsibility in a similar construction
• Both are prayers
• The opening is past; the ending future
• The ending means only travelling