Verb douleuō (to serve, to be enslaved) in the New Testament

(Translation from NRSV with a few modifications for a more literal meaning)

Matthew

6: 24"No one can serve (douleuō) two masters; for a slave will either hate the one and love the other, or be devoted to the one and despise the other. You cannot serve (douleuō) God and wealth.

Luke

15: 29But he answered his father, 'Listen! For all these years I have been serving (douleuō) you, and I have never disobeyed your command; yet you have never given me even a young goat so that I might celebrate with my friends.
16: 13No slave can serve (douleuō) two masters; for a slave will either hate the one and love the other, or be devoted to the one and despise the other. You cannot serve (douleuō) God and wealth."

John

8: 33They answered him, "We are descendants of Abraham and have never been enslaved (douleuō) to anyone. What do you mean by saying, 'You will be made free'?"

Acts

7: 7'But I will judge the nation that they serve (douleuō),' said God, 'and after that they shall come out and worship me in this place.'
20: 19serving (douleuō) the Lord with all humility and with tears, enduring the trials that came to me through the plots of the Jews.

1 Thessalonians

1: 9For the people of those regions report about us what kind of welcome we had among you, and how you turned to God from idols, to serve (douleuō) a living and true God,

Philippians

2: 22But Timothy's worth you know, how like a son with a father he has served (douleuō) with me in the work of the gospel.

Galatians

4: 8Formerly, when you did not know God, you were enslaved (douleuō) to beings that by nature are not gods.
4: 9Now, however, that you have come to know God, or rather to be known by God, how can you turn back again to the weak and beggarly elemental spirits? How can you want to be enslaved (douleuō) to them again?
4: 25Now Hagar is Mount Sinai in Arabia and corresponds to the present Jerusalem, for she is inslaved (douleuō) with her children.
5: 13For you were called to freedom, brothers and sisters; only do not use your freedom as an opportunity for self-indulgence, but through love serve (douleuō) one another.

Romans

6: 6We know that our old self was crucified with him so that the body of sin might be destroyed, and we might no longer be enslaved (douleuō) to sin.
7: 6But now we are discharged from the law, dead to that which held us captive, to serve (douleuō) not under the old written code but in the new life of the Spirit.
7: 25Thanks be to God through Jesus Christ our Lord! So then, with my mind I am serving (douleuō) the law of God, but with my flesh the law of sin.
9: 12not by works but by his call) she was told, "The elder shall serve (douleuō) the younger."
12: 11Do not lag in zeal, be ardent in spirit, serve (douleuō) the Lord.
14: 18The one who thus serves (douleuō) Christ is acceptable to God and has human approval.
16: 18For such people do not serve (douleuō) our Lord Christ, but their own appetites, and by smooth talk and flattery they deceive the hearts of the simple-minded.

Colossians

3: 24since you know that from the Lord you will receive the inheritance as your reward; you serve (douleuō) the Lord Christ.

Ephesians

6: 7Serve (douleuō) with enthusiasm, as to the Lord and not to men and women,

1 Timothy

6: 2Those who have believing masters must not be disrespectful to them on the ground that they are members of the church; rather they must serve (douleuō) them all the more, since those who benefit by their service are believers and beloved. Teach and urge these duties.

Titus

3: 3For we ourselves were once foolish, disobedient, led astray, being slaves (douleuō) to various passions and pleasures, passing our days in malice and envy, despicable, hating one another.