Here in Alma 58:3, the editors for the 1920 LDS edition removed the clause-initial of the from the rather awkward relative clause “of the which we had retained of our possessions”. One could argue that the extra of the was due to the of the in the preceding noun phrase, “those parts of the land”. The 1920 change is probably the best possible minimal emendation for making the text conform to standard literary English.
Despite the 1920 emendation, the resulting relative clause still reads awkwardly. Another possible emendation would have been more drastic: change the relative clause by replacing the phrase “of our possessions” with the simple noun possession, thus “those parts of the land of the which we had retained possession” or (more smoothly) “those parts of the land which we had retained possession of”, as elsewhere in the text:
Alma 58:3 is extant in the original manuscript. As explained under 2 Nephi 3:14, there are similar examples of this kind of awkward usage in the original text, so the usage here in Alma 58:3 may be intended and will therefore be restored in the critical text.
Summary: Restore in Alma 58:3 the original reading with its awkward of the which at the beginning of the relative clause (“those parts of the land of the which we had retained of our possessions”); although awkward, other examples in the original text support this usage, which in this case is extant in 𝓞.