大乘起信論廣釋卷第三．四．五 5.77

5.77

Treatise: "One should know that tathatā... immeasurable samādhis."
Commentary: This shows that tathatā is the basis of samādhi. This means that this tathatā is the essence of samādhi, and samādhi is the cause of tathatā. All samādhis are produced in accordance with truth; therefore, it says that tathatā is the basis of samādhi. Since tathatā is the root of samādhi, practicing in reliance on truth is called the tathatā-samādhi. Based on this, many samādhis are further produced, because this contemplates the essence of tathatā-samādhi. One who attains this attains the root place of samādhis. Therefore the purport of the new and old treatises is identical, differing only in the sequence of the text.