俱舍論疏 12.54

12.54

論「如何不許至發長時願」，答。無上菩提甚難得故，彼若不能發長時願修多苦行等不得菩提，是故定須發長時願。

On the Śāstra's text, "How could one not accept that... makes vows of long duration": The answer. Because unexcelled bodhi is extremely difficult to attain, if one cannot make vows of long duration and cultivate many austerities and so forth, one will not attain bodhi; therefore, one definitely must make vows of long duration.