جَدَّ جِدُّهُ
His exertion became intense; literally, his earnest effort itself strove.
The person is the one who exerts effort. Yet jidd (جِدّ), the verbal noun or concept of exertion, appears as the grammatical doer of the verb. The semantic event has been assigned to a closely connected action-noun rather than to the person.
The expression gives rhetorical force to the degree of effort. It also shows that rational figurative predication can occur with an overt verb, not only adjectival participles.