John Gill

But unto them that are contentious,.... This is a description of the other sort of persons to whom God will render according to their deeds, "who are of the contention"; who contend for victory, and not truth; strive about words to no profit; are quarrelsome, and sow discord among men, and in churches; and do not obey the truth; neither attend to the light of nature, and to that which may be known of God by it; nor regard and submit to the Gospel revelation and so design both the Gentiles, which knew not God, and Jews, and others, who obey not the Gospel: but obey unrighteousness; are servants of sin: to these God renders indignation and wrath; wrathful or fiery indignation, the hottest of his fury.