The Companion Bible E.W.Bullinger:
Verse 36 And out of the tribe of Reuben. See note on Joshua 21:38 .
Reuben. Some codices, with one early printed edition, add "a city of
refuge for the manslayer
Bezer . Some codices, with Septuagint and Vulgate, add in the desert".
and Jahasah . Some codices omit this "and"
Verse 37 Kedemoth. Some codices, with six early printed editions, and
Septuagint, read "and Kedemoth
By an Homoceoteleuton ( App-6 )
Ho´-mœ-o-tel-eu´-ton; or, Like Endings (Mark 12:30). The repetition of
the same letters or syllables at the end of successive words. Used
also of an omission in the text caused by such-like endings: the
scribe's eye going back to the latter of such similar words, instead
of the former. See Joshua 2:1.
some scribe, writing as far as "four cities "at end of Joshua 21:35 , went back with his eye to the same words at the end of Joshua 21:37 , and omitted, by an accident, the two verses Joshua 21:36 and Joshua 21:37 , and continued at Joshua 21:38 , which commences with the some words which end Joshua 21:35 . Hence they are not contained in the current text of the Hebrew Bible.
The Authorized Version puts these verses in, however, without a note; the Revised Version also, but with a note. The two verses are contained in all the early printed Hebrew Bibles, the Septuagint and Vulgate, and very many codices.
They were first omitted by Jacoh ben Chayim (1524, 1525), and the current Hebrew printed texts have followed him.