Joshua 24:19

And Joshua said unto the people, Ye cannot serve the LORD: for he is an holy God; he is a jealous God; he will not forgive your transgressions nor your sins.

Joshua spoke these words when he had gathered Israel and its leaders together after the wars of conquest had ended and the Lord had given the people rest from their enemies. In this farewell setting he reviewed God's care for Israel and warned the people against idolatry and close ties with idolaters, including intermarriage, because these would corrupt them and lead them away from God. The warning calls for shunning even the appearance of evil and not approaching the borders of sin, since departure from God would bring desolation. As God had been faithful to fulfill His promises, so He would be faithful to carry out His warnings. That warning applies to each person individually.

The people could not serve the Lord by themselves because He is holy and His perfect law condemned them as transgressors with no way of escape. As long as they trusted in their own strength and righteousness they could not meet God's claims nor secure pardon for sin, so their pledge and promises to serve God were vain and could not make them acceptable or earn forgiveness. Before lasting reformation could come, they had to feel their utter inability to render obedience.

They could not truly serve the holy God while continuing in sin, for God is perfectly true and holy and cannot join with iniquity. The natural heart is a field of conflict between conscience and passion, and persistent transgression keeps people from receiving God's favor and support. Only thorough repentance and a changed life can restore His favor. Those who honor God are honored by Him, but those who forsake Him for other gods are forsaken by Him. Pardon of sin and strength to obey God's law come only by faith in Christ and reliance on the merits of the promised Saviour. That faith means ceasing to rely on one's own righteousness, turning from idolatry, and trusting wholly in the Saviour in order to be accepted by God.