'Serve the Lord' in the Bible
“Now, therefore, fear the Lord and serve Him in sincerity and in truth; remove the gods which your fathers served on the other side of the [Euphrates] River and in Egypt, and serve the Lord.
If it is unacceptable in your sight to serve the Lord, choose for yourselves this day whom you will serve: whether the gods which your fathers served that were on the other side of the River, or the gods of the Amorites in whose land you live; but as for me and my house, we will serve the Lord.”
The Lord drove all the peoples out from before us, even the Amorites who lived in the land. We also will serve the Lord, for He is our God.”
Then Joshua said to the people, “You will not be able to serve the Lord [if you serve any other gods], for He is a holy God; He is a jealous God [demanding what is rightfully and uniquely His]. He will not forgive your transgression [of His law] or your sins.