Matthew 4:10

then Jesus saith unto him, Be gone, Satan; for it is written, Thou shalt worship the Lord thy God,

Luke 4:8

And Jesus answering him said with indignation, Get thee behind me, Satan: for it is written, Thou shalt worship the Lord thy God, and Him only shalt thou serve.

Matthew 6:24

No one can serve two masters; for either he will hate the one, and love the other; or at lest he will be attached to the one, and neglect the other: ye cannot serve God and mammon:

Matthew 15:8

saying, This people approach me with their mouth, and honour me with their lips, but their heart is far from me:

John 4:24

God is a spirit, and they that 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
saying, This people approach me with their mouth, and honour me with their lips, but their heart is far from me:
John 4:24
God is a spirit, and they that worship Him, must worship in spirit and truth.

Serve him

Matthew 4:10
then Jesus saith unto him, Be gone, Satan; for it is written, Thou shalt worship the Lord thy God,
Matthew 6:24
No one can serve two masters; for either he will hate the one, and love the other; or at lest he will be attached to the one, and neglect the other: ye cannot serve God and mammon:
Luke 4:8
And Jesus answering him said with indignation, Get thee behind me, Satan: for it is written, Thou shalt worship the Lord thy God, and Him only shalt thou serve.