For there were many in the assembly who had not sanctified themselves: Among the ordinary people present for the Passover celebration, there were many who had failed to go through the proper ritual cleansing required. The Hebrew particle rendered For introduces this clause as the reason for what follows.

Therefore the Levites had to kill the passover lamb for every one who was not clean: According to the Law of Moses, the heads of families were to kill the Passover lambs (see Exo 12.1-6). But since many of the people, perhaps especially those who came from the north, were not ritually clean, the Levites killed the lambs for them. The passover lamb is literally “the passovers,” so this expression is better rendered “the Passover lambs” (Good News Translation; see the comments on verse 15). Everyone who was not clean refers to all the people who were unacceptable because they had not undergone the proper ritual cleansing.

To make it holy to the LORD may be rendered “to set them [the lambs] apart for the LORD” (New Living Translation).

Quoted with permission from Omanson, Roger L. and Ellington, John E. A Handbook on 1-2 Chronicles, Volume 1. (UBS Helps for Translators). Miami: UBS, 2014. For this and other handbooks for translators see here .