Job 32:18 - Matthew Poole's English Annotations on the Holy Bible

I am full of matter, i.e. I have many things to say in this cause. The spirit within me; either my own spirit or soul, which is wholly dissatisfied with what hath been hitherto spoken, and clearly apprehends what may silence Job, and end the dispute; or God's Spirit, which he hath put in me; the Spirit of understanding, which hath discovered the truth of the matter to me; and the Spirit of zeal, which urgeth me to plead God's cause against Job. Constraineth me; forceth me to speak. It is a metaphor from a man or woman whose belly is full with wind, or with a child, and is never at rest till it be emptied and eased of its burden.