'Priest's' in the Bible

Now it happened, while he executed the priest's office before God in the order of his division,

according to the custom of the priest's office, his lot was to enter into the temple of the Lord and burn incense.

They seized him, and led him away, and brought him into the high priest's house. But Peter followed from a distance.

Simon Peter therefore, having a sword, drew it, and struck the high priest's servant, and cut off his right ear. The servant's name was Malchus.

They indeed of the sons of Levi who receive the priest's office have a commandment to take tithes of the people according to the law, that is, of their brothers, though these have come out of the body of Abraham,