'Serve the Lord' in the Bible

Mary said, "I am here to serve the Lord. Let it be as you have said." Then the angel went away.

to serve the Lord with all humility and in tears, through the trials that befell me because of the plots of the Jews.

Do not lack diligence; be fervent in spirit; serve the Lord.

It is in your own interest that I say this; not that I may entangle you in a snare, but that I may help you to serve the Lord with fitting and undistracted service.

Knowing that of the Lord ye shall receive the reward of the inheritance: for ye serve the Lord Christ.