大乘起信論義疏 1.37

1.37

自下第四轉釋。此義云何？何故二門各攝一切法者，一心二義故，故言「是二門不相離故」也。義分為二：非是別體故言「不離」。

Below, the fourth is the further explanation. What does this mean? Why do the two doors each encompass all dharmas? Because of the two meanings of the one mind, it says: "because these two doors are not separate from each other." The meanings are divided into two; because they are not distinct substances, it is said that they "are not separate."