Joshua 24:19 - Ellicott's Commentary On The Whole Bible

And Joshua said... Ye cannot serve the Lord: for he is... jealous... — Jehovah will not consent to be served as one God among many: the very thing which Israel was doing at the moment, which they meant to do, and did do, with rare intervals, down to the Babylonish captivity, when the evil spirit of (literal) idolatry was expelled for evermore. Israel always maintained the worship of Jehovah (except in very evil times) as the national Deity, but did not abstain from the recognition and partial worship of other national deities of whom they were afraid, and whom they thought it necessary to propitiate. Therefore Joshua’s argument is perfectly intelligible, and was entirely necessary for those times.