Matthew 4:10
If having fallen down thou mayest worship me: then Jesus says to him, Get behind me, Satan; for it has been written; Thou shalt worship the Lord thy God, and Him only shalt thou serve.
Luke 4:8
And Jesus responding said to him; It has been written, Thou shalt worship the Lord thy God and Him only shalt thou serve.
Matthew 6:24
No one is able to serve two masters: for he will hate the one, and love the other; or cleave to the one, and despise the other. You are not able to 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 it behooveth those who worship Him to worship in spirit and in truth.