坐禪三昧經 2.34

2.34

復次。懃精進一心入涅槃道中，更了了觀五陰、四諦十六行。是時，心不縮不悔不退，愛樂入忍，是名忍善根。忍何等？隨四諦觀行，是名為忍。是善根三種：上、中、下三時。

Furthermore, with zealous vīrya and single-mindedness entering the path of nirvāṇa, he contemplates even more clearly the five aggregates and the sixteen aspects of the four truths. At this time, his mind does not shrink, does not regret, and does not regress; loving and delighting [in them], he enters acceptance (kṣānti). This is named the root of goodness of acceptance. What does he accept? He accords with the contemplation and practice of the four truths; this is named acceptance. This root of goodness is of three kinds: the three stages of superior, middling, and inferior.