Ver. 19. And Joshua said unto the people, ye cannot serve the Lord, &c.— These words may he understood two ways. 1. They may signify, "you will not serve the Lord; I foresee that ye will not keep your word:" in the same sense as it is said of Jesus Christ, that he could work no miracle at Nazareth, to express that he would not; or, as when he said to the Jews, ye cannot hear my word; i.e. your prejudices and passions hinder you from desiring it. 2. They may signify "the thing is difficult, it requires great courage, and will cost you more than you are aware, by reason of the temptations you will have to conquer in the attaining it." These two senses seem necessary to be united for the proper understanding of the passage. The intention of Joshua is certainly, not to insinuate to the Israelites that it will be impossible for them to serve God; for why then should he have exhorted them to serve him, as he had just done in ver. 14.? His design is evident: it is, to pique the zeal of the Israelites, to engage them seriously to reflect on what they promised, and to stimulate their protestations of fidelity, by seeming to doubt the sincerity of them: as if he had said, "You promise to serve God; but can you do so, whose inclinations to idolatry are so strong? And will you be firm and courageous enough to persevere sincerely in the desire so to do?"
For he is an holy God; he is a jealous God, &c.— As he has no equal, neither can he suffer a rival. To pay to idols that worship which he only deserves, or even to associate them with the homage which is paid to him, is to contest with him, to take from him a part of that perfect holiness which constitutes his glory, and is what the Scripture calls profaning his holy name. See Mede's Discourses, b. 1: disc. 2.