The poetry of Isaiah and David would have been poetry without a single parallelism.
"The Literature of Ecstasy"
Albert Mordell
If this definition were true, then passages in the Bible full of poetry, which use no parallelism, would not be poetry.
"The Literature of Ecstasy"
Albert Mordell
In short, we have the beginning of parallelism.
"The Literature of Ecstasy"
Albert Mordell