When you and I encounter the word “poetry” we immediately think of something read, sung, or listened to that rhymes. If we studied poetry academically, we’d learn that there’s a lot more to poetry as we know it, but rhyming is our most familiar experience of the concept.
Because we think of poetry this way, it’s hard for us to see why Psalms, Proverbs, and other portions of the Bible are classified as poetry. Like English, a line of Hebrew poetry is broken down into smaller units called cola. “Mary had a little lamb // its fleece was white as snow” is a complete line made up of two parts (two cola). But that’s really where the similarity ends. The fundamental difference in Hebrew poetry and what we think of with respect to that term is that Hebrew poetry doesn’t rhyme in sound. It rhymes in thought.
This concept of “thought rhyming” is called parallelism. In simplest terms, a line of Hebrew poetry (e.g., Ps. 2:4) can begin with a colon (“The one who rules in heaven laughs”), which is followed by another colon that expresses a similar thought (“The Lord scoffs at them”). The relationship between the two cola is the important item for interpretation. The second colon corresponds to the first in some way. The second element advances the thought of the first. There is a symmetrical relationship in the thought expressed.
This “thought rhyming” can be accomplished in a variety of ways. Sometimes colon two is virtually synonymous with colon one. Perhaps only the vocabulary varies. The example from Psalm 2:4 above fits that description. Sometimes a series of cola will build to a climactic conclusion. On other occasions, the second colon expresses the thought of the first in an inverted way. For example, Psalm 1:6 says,
(colon 1): For the LORD knows the way of the righteous,
(colon 2): but the way of the wicked will perish.
The two thoughts here are consistent with one another, but they are like two sides of a coin. By definition if the wicked perish, that fate will not befall the righteous.
Grasping the range of possible “thought rhyme” strategies used in Psalms and Proverbs takes time, close reading, and careful thought. Study Bibles and other books help by providing brief introductions to the techniques with examples. Making an effort to learn about parallelism will provide insight into your reading of those books and help you avoid drawing poor conclusions about interpretation.