成唯識論演祕 2.237

2.237

答：傳有三釋：一云，通防三世，過、未雖無，依現立故，故防現在義即防三。二云，唯防現在，過、未無故。三云，唯防未來，過、現已起，防無用故。

Answer: Tradition transmits three explanations: (1) It says that it generally prevents across the three periods of time; although past and future do not exist, because they are established on the basis of the present, preventing the present means in principle preventing the three. (2) It says that it prevents only the present, because past and future do not exist. (3) It says that it prevents only the future, because past and present have already arisen, and preventing them would be useless.