首楞嚴義疏注經 6.422

6.422

殺生、偷盜執對不亡，為三界緣，障菩提路。然身苦體能報此因，宿債苟除，世間永脫，故云長揖。

When clinging to the confrontation of killing and stealing is not destroyed, it forms conditions with the three realms and obstructs the path to bodhi. Burning the body and suffering in the physical form can repay this cause; if past debts are eliminated, one is forever free from the world; hence it says 'make a permanent farewell.'