Chapters 17 to 26 read differently from what precedes them, and the difference is consistent enough that scholars treat the block as a separate composition, designated H against the priestly material designated P. It was identified as a distinct unit in the late nineteenth century and the identification has held.
Three things mark it. The refrain you shall be holy, for I the Lord your God am holy recurs through it and appears nowhere in the earlier chapters. The address widens: where chapters 1 to 16 mostly instruct priests, this block speaks to the whole community, and holiness becomes something a farmer or a creditor can practise. And the subject matter turns social. The jubilee, in which land returns to its original holding, is here. So is the sabbatical year, the prohibition on charging interest to the poor, the command to leave the edges of a field unharvested for the destitute, the requirement to pay a labourer before nightfall, and the instruction to love your neighbour as yourself, which appears at chapter 19 and again a few verses later extended to the foreigner resident among you.
Where the block sits in the history of the text is still argued. The older view treated H as an earlier collection that P later absorbed. A substantial body of more recent work reverses that, reading H as the later editorial layer that framed the priestly material and gave the whole book its ethical range. The two readings produce different pictures of what the priesthood was for, and the evidence has not settled the matter.