'Porters' in the Bible

This is the thing that ye shall do: a third part of you, that come in on the sabbath, of the priests and of the Levites, shall be porters of the thresholds;

And he set the porters at the gates of the house of Jehovah, that none that was unclean in anything should enter in.

Also they were over the bearers of burdens, and set forward all that did the work in every manner of service: and of the Levites there were scribes, and officers, and porters.

And the singers the sons of Asaph were in their place, according to the commandment of David, and Asaph, and Heman, and Jeduthun the king's seer; and the porters were at every gate: they needed not to depart from their service; for their brethren the Levites prepared for them.