How many cords does "P'sil Texheiles" incorporate?
Rashi (in Pikudei): There must have been at least two cords to tie the Choshen to the Eifod via the rings on the two sides (at the top and at the bottom). 1
See Rashi in Pikudei, 39:31.
What is the meaning of the word "Lo Yizach"?
Rashi 31 (citing Dunash ben Lebret) , Targum Onkelos and Targum Yonasan: It is an Arabic word that means 'it shall not move away (become detached').
Rashi (in Pasuk 32): It is a La'av against separating the Choshen from the Eifod (which is subject to Malkos - Yoma, 73b). 1
Ramban: Based on the fact that a "Zayin' and a "Samech' are interchangeable, 2 it means 'demolish (break-up') - like 'Lo Yisach ... '.
See Torah Temimah, note 8.
Like we find "Ya'alzu Chasidim be'Chavod" (Tehilim, 149:5) is like "Nis'alsah ba'Ahavim" (Mishlei, 7:18) and "Ve'nitatztem es Mizbechosam" (Devarim 12:3) is like "Zadon Shabbos Nesivasi" - Iyov, 30:13 (Ramban).
Why is it forbidden to move the Choshen from the Eifod?