Rashi on Numbers 33:55/רש"י על במדבר ל״ג:נ״ה

1והיה אשר תותירו מהם THEN IT SHALL COME TO PASS THAT THOSE WHOM YE LEAVE OF THEM shall be a misfortune for you.

2לשכים AS שכים IN YOUR EYES — as pins which prick out your eyes: the Targum translation of יתדות pins or pegs, is שיכיא (cf. e. g., Exodus 27:19).

3ולצנינים — The lexicographers explain it in the sense of a hedge of thorns (צנינים is another form of צנים) so that the meaning here is: they will become as something which hedges you in, enclosing and imprisoning you in order that none can go forth nor come in (cf. Rashi on Joshua 23:13) (The meaning is they will hedge you in on all sides בצדיכם.

4וצררו אתכם — Understand this as the Targum does: (“and they will distress you”).