because a great number were not sanctified. And therefore, the Levites immolated the Passover for those who had not been sanctified to the Lord in time
Other versions
King James Version
For there were many in the congregation that were not sanctified: therefore the Levites had the charge of the killing of the passovers for every one that was not clean, to sanctify them unto the LORD.English Standard Version
For there were many in the assembly who had not consecrated themselves. Therefore the Levites had to slaughter the Passover lamb for everyone who was not clean, to consecrate it to the LORD.New International Version
Since many in the crowd had not consecrated themselves, the Levites had to kill the Passover lambs for all those who were not ceremonially clean and could not consecrate their lambs to the LORD.