Joshua 24:14 Now therefore fear the Lord, and serve him in sincerity and in truth: and put away the gods which your fathers served on the other side of the flood, and in Egypt, and serve ye the Lord.
Joshua was afraid that the people would forget the Lord and start worshipping false gods and idols, so he gives them this further encouragement before he dies. And so it happened that, after Joshua and the elders had passed on, Israel fell into idolatry and as a result suffered at the hands of enemies many times during the period of the Judges. And time and again God rescued them.
To respond with the fear of the Lord is to believe Him so firmly and to love Him
so strongly that we have a deep inner desire serve Him by keeping His Commandments. Serving means honoring the Lord as the One True God, trusting His love to forgive us and restore us to a loving relationship with Him. Our response to the gospel is: “Worship the Lord your God and serve Him only.” Serve means worship, listen to, and believe in our Savior God alone. God does need our service, but other people do. Serve God by serving people. Therefore, out of the believing reception of free salvation we gladly and eagerly “love our neighbor as ourself.”
Worshipping the Lord in sincerity and in truth requires putting away other gods or anything else of the world that we look to for happiness and well-being. Israel’s fathers worshipped the gods of Old Babylon (beyond the Euphrates) until God called Abraham, and the gods of Egypt until God called Moses.
Our Lord is an exclusive God, who is so holy and loving that He cannot allow the fear of, love for, trust in, hope in, and seeking for life from any other source, especially from one’s self. The Lord saves; therefore we fear Him alone.