Some take the three final verses as an expression of assurance, in which the poet finally speaks his certain assurance that the Lord will judge his enemies. Others take them as prayers.
The group who takes them as assurances do so because of the verb forms. When the form of the verbs is considered, it seems better to regard them as positive expressions. That what is spoken shall come about. When Lamentations 3:64 is compared with Psalm 28:4, this viewpoint is reinforced as the same idea, although somewhat more elaborated, occurs there, although in the form of a prayer. The writer is convinced that God will repay his enemies. He is assured of prompt and accurate retribution.1
The other group sees this stanza as a prayer that the Lord will let justice prevail by punishing the enemies according to their deeds. (This group would also refer to Psalm 28:4). He asks that God should pursue them in his wrath and cast them out from under his heaven.2 Continuing the pattern of the previous verses, it could be understood as the continuation of a prayer to God.
Although there are the above-mentioned two viewpoints, it is not necessary to choose between them. While the verbs in these verses are all in the imperfect tense, they may be understood both ways: It does express confidence in God that he will deal with the enemies, but it could also be understood simultaneously as a prayer that he will do so. Both options suit the contexts. Because of the assurance that God has acted in the past, the writer is now also assured that God will act, and therefore urges God to do so.3
64 “You will repay them, O LORD, according to the work of their hands.