'Serve' in the Bible

Some time later Absalom managed to acquire a chariot and horses, as well as fifty men to serve as his royal guard.

For I made this vow when I was living in Geshur in Aram: 'If the Lord really does allow me to return to Jerusalem, I will serve the Lord.'"

Moreover, whom should I serve? Should it not be his son? Just as I served your father, so I will serve you."