There are a number of factors that must be considered when we are looking at verses such as Lamentations 3:37-38. The first is, where are the verses found? In this case, Lamentations is in the Old Testament, not in the New Testament. We know the world is a war zone between God and the Devil, and God is trying to do good while the Devil is working from an evil agenda. However, the conflict between God and the Devil is not clearly revealed in the Old Testament while it is in the New Testament. Jesus spoke of this fact in Luke 10:23-24. The Old Testament generally shows God being in control of both good and evil as it does here and in other places.
Another thing that we must be aware of is “who is speaking?” In this case, the writer Jeremiah is speaking, which is clear from the context. Jeremiah, like Job and the other Old Testament believers, generally thought that God was in control of both good and evil, and so it is perfectly natural that he would express that fact.
These verses are a good example why we must examine the whole Bible in order to get a proper understanding about God. These verses clearly show us what the people of Jeremiah’s time thought, but they do not clearly reveal the truth about the goodness of God like the New Testament does.