大乘起信論裂網疏 2.29

2.29

言真實不空者，由妄念空無故，即顯真心常恒不變，淨法圓滿，故名不空。亦無不空相，以非妄念心所行故，唯離念者之所證故。

"As for what is called genuinely non-empty: because deluded thoughts are empty and non-existent, the true mind is revealed to be eternal and immutable, replete with pure dharmas; hence it is called non-empty. Yet it also has no mark of non-emptiness, because it is not an object traversed by the mind of deluded thoughts, and is realized only by those who are free from thoughts."