俱舍論記 4.203

4.203

「此由所依至但假非實」者，經部釋。斷、未斷由治道力，令所依身無復功能令其現起，名為斷、名不成就。與此相違，名為未斷、名為成就。若聖道力畢竟斷故名斷，若世間道損伏斷故名斷。成與不成皆假非實，昔有惑種，今斷即無，故名轉變異本。

Regarding 'This is because the basis... only nominal, not real': the Sautrāntika explains. Severed and unsevered occur because through the power of the antidotal path, the basis—the personal continuum—no longer possesses the capacity to make them arise, and this is called 'severed' and 'non-possession'. The opposite of this is called 'unsevered' and 'possession'. If by the power of the noble path they are completely severed, it is called 'severed'; if by the power of the mundane path they are suppressed and severed, it is called 'severed'. Both possession and non-possession are merely nominal and not real. Formerly there were seeds of defilement, but now with severance they no longer exist; hence it is called 'transformation into a different nature'.