首楞嚴義疏注經 8.153

8.153

隨機、隨感現種類身，盡未來際化復作化。三世下釋所以也，以知三世空寂故，得窮未來際；以達十方無礙故，能現種類身。若時、若處現化不絕，故云無盡也。

In accordance with capacities and in accordance with responsiveness, he manifests bodies of all species, exhausting the bounds of the future in performing transformations upon transformations. From 'the three periods of time' downward, it explains the reason: because he knows that the three periods of time are empty and tranquil, he can exhaust the bounds of the future; because he penetrates the ten directions without impediment, he can manifest bodies of all species. Whether in terms of time or in terms of place, manifesting transformations is uninterrupted; hence it is called 'inexhaustible.'