serve

first come, first served: seefirst.

serve someone right be someone's deserved punishment or misfortune.

serve your time

1 hold office for the normal period.

2 spend time in office, an apprenticeship, or prison.

serve your (or its) turn be useful or helpful.

serve two masters take orders from two superiors or follow two conflicting or opposing principles or policies at the same time.

☞ This phrase alludes to the warning given in the Bible against trying to serve both God and Mammon (Matthew 6:24).