Charles Ellicott Commentary Joshua 24:19

"And Joshua said unto the people, Ye cannot serve Jehovah; for he is a holy God; he is a jealous God; he will not forgive your transgression nor your sins." — Joshua 24:19 (ASV)

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