Sforno on Deuteronomy 4:24/ספורנו על דברים ד׳:כ״ד

1אש אוכלה הוא, a fire which consumes other fire, thereby destroying the soul together with the body.

2א-ל קנא, [I am paraphrasing the author here. Ed.] Jealousy is based on someone observing that something contractually exclusively his, as for instance the, fidelity of his wife- is being offered or provided for someone else. If a master’s servant provides the services he is supposed to provide only for his master to others, this arouses the master’s jealousy. If a Jew in any shape or form makes available to idolatrous cults the services he is supposed to perform for G’d, he arouses G’d’s jealousy.