Job 15:25 - Matthew Poole's English Annotations on the Holy Bible

Now he gives the reason of all the forementioned calamities which befell him, which was his great wickedness in the time of his peace and prosperity. He stretcheth out his hand against God, i.e. he commonly and customarily sinned against God with a high and out-stretched hand, i.e. boldly and presumptuously, as one that neither desired his favour, nor feared his anger. Strengtheneth himself, i.e. he putteth his forces in array, as if he would fight with him. Against the Almighty; which aggravates the madness of this poor contemptible worm that durst fight against the omnipotent God.