Matthew 4:10

"Begone, Satan!" answered Jesus, for it is written, "Thou must worship the Lord thy God, and Him only must thou serve."

Luke 4:8

"It is written," answered Jesus, "Thou shalt worship the Lord, thy God, and him only shalt thou serve."

Matthew 6:24

"No slave can serve two masters, for either he will hate the one and love the other, or he will pay heed to the one and despise the other. You cannot be the slaves both of God and of gold.

Matthew 15:8

This is a people that honors me with their lips, But their heart is far from me.

John 4:24

God is spirit, and those who worship him must worship him in spirit and in truth."

Treasury of Scripture Knowledge

Summary

And Samuel spake unto all the house of Israel, saying, If ye do return unto the LORD with all your hearts, then put away the strange gods and Ashtaroth from among you, and prepare your hearts unto the LORD, and serve him only: and he will deliver you out of the hand of the Philistines.

Bible References

Prepare

Matthew 15:8
This is a people that honors me with their lips, But their heart is far from me.
John 4:24
God is spirit, and those who worship him must worship him in spirit and in truth."

Serve him

Matthew 4:10
"Begone, Satan!" answered Jesus, for it is written, "Thou must worship the Lord thy God, and Him only must thou serve."
Matthew 6:24
"No slave can serve two masters, for either he will hate the one and love the other, or he will pay heed to the one and despise the other. You cannot be the slaves both of God and of gold.
Luke 4:8
"It is written," answered Jesus, "Thou shalt worship the Lord, thy God, and him only shalt thou serve."