Albert Barnes Commentary Job 32:18

"For I am full of words; The spirit within me constraineth me." — Job 32:18 (ASV)

For I am full of matter - Margin, as in Hebrew, "words." The three friends of Job had been silenced. They had not one word more to say. Elihu says that the reverse was true of him. He was full of words and felt compelled to speak. It was not because he forced himself to do it, nor because he did it merely as a matter of duty, but he was so impressed with the subject that it would be a relief for him to express his views.

The spirit within me - This refers, probably, to the conviction that it was the divine Spirit who urged him to speak (see the notes on Job 32:8). A similar constraint regarding the necessity of speaking, when under the influence of the Holy Spirit, is expressed in Jeremiah 20:9: "His word was in my heart as a burning fire shut up in my bones, and I was weary with forbearing, and I could not stay"; (compare the Introduction to Isaiah, Section 7).

The phrase "within me" is in the margin (as in Hebrew, "my belly")—where the belly is spoken of as the seat of the mind . We speak of the head as the seat of the intellect and the heart as the seat of the affections. The Hebrews were much in the habit of representing the region of the heart as the seat of all mental operations.