'Pollutions' in the Bible

Only the Levites shall perform the service of the Tent of Meeting (tabernacle), and they shall bear their iniquity; it shall be a statute forever throughout your generations, that the Levites shall have no inheritance [of land] among the children of Israel.

The Passover was eaten by the sons (descendants) of Israel (Jacob) who returned from exile and by all those who had separated themselves from the [ceremonial] uncleanness of the nations of the land to join them, in order to seek the Lord God of Israel.

which You have commanded by Your servants the prophets, saying, ‘The land which you are entering to possess is a defiled land with the uncleanness of the peoples of the lands, through their repulsive acts which have filled it from one end to the other along with their impurity.

For if, after they have escaped the pollutions of the world by [personal] knowledge of our Lord and Savior Jesus Christ, they are again entangled in them and are overcome, their last condition has become worse for them than the first.