Matthew 4:10

Then Jesus saith to him, "Depart, Satan; for it has been written, 'You shall worship the Lord your God, and Him only shall you serve.'"

Luke 4:8

And Jesus, answering, said to him, "It has been written, 'You shall worship the Lord your God, and Him only shall you serve.'"

Matthew 6:24

"No one can serve two masters; for either he will hate the one, and love the other; or he will hold to one, and despise the other. Ye cannot serve God and Mammon.

Matthew 15:8

'This people honor Me with their lips, but their heart is far from Me.

John 4:24

God is a spirit; and those who worship Him must worship in spirit and 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 people honor Me with their lips, but their heart is far from Me.
John 4:24
God is a spirit; and those who worship Him must worship in spirit and truth."

Serve him

Matthew 4:10
Then Jesus saith to him, "Depart, Satan; for it has been written, 'You shall worship the Lord your God, and Him only shall you serve.'"
Matthew 6:24
"No one can serve two masters; for either he will hate the one, and love the other; or he will hold to one, and despise the other. Ye cannot serve God and Mammon.
Luke 4:8
And Jesus, answering, said to him, "It has been written, 'You shall worship the Lord your God, and Him only shall you serve.'"