Matthew 4:10

Then Jesus said to him, "Away, Satan! for it is written, 'You shall worship the Lord your God and him only shall you serve.'"

Luke 4:8

And Jesus answered him, "It is 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 be devoted to the one and despise the other. You cannot serve God and mammon.

Matthew 15:8

'These people honor me with their lips, but their heart is far from me.

John 4:24

God is 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
'These people honor me with their lips, but their heart is far from me.
John 4:24
God is spirit, and those who worship him must worship in spirit and truth."

Serve him

Matthew 4:10
Then Jesus said to him, "Away, Satan! for it is 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 be devoted to the one and despise the other. You cannot serve God and mammon.
Luke 4:8
And Jesus answered him, "It is written, 'You shall worship the Lord your God, and him only shall you serve.'"