俱舍論記 17.33

17.33

「有餘師說至未易捨故」者，此釋二俱捨。一敘異說、二申正義，此敘異說。因彼善根發得律儀，故善根是本、律儀是末。末易捨故所以先捨，本難捨故所以後斷。

Regarding "Other masters say ... because it is not easy to abandon": This explains the abandonment of both. First, a different view is relayed; second, the correct doctrine is presented. This relays the different view. Restraint is generated based on those wholesome roots; therefore the wholesome root is the root and restraint is the branch. Because the branch is easily abandoned, it is abandoned first; because the root is difficult to abandon, it is severed later.