大乘起信論廣釋卷第三．四．五 5.77

5.77

論。當知真如至無量三昧　釋曰。此顯真如為三昧本。謂此真如是三昧體。三昧乃是真如之因。一切三昧隨真而生故。說真如為三昧本。真如既是三昧根本。若依真修行名真如三昧。依此復生多諸三昧。此觀真如三昧體故。得者其三昧根本處。故訴論意同但文前後。

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.