大方廣佛華嚴經隨疏演義鈔 25.28

25.28

疏「真如即是不空」者，此言不空，自有二義：一空者，所謂生死。不空者，是謂大涅槃。二對下空藏，是不空藏，妙有之中含性德故。

On the commentary's "Tathatā is precisely the non-empty": this statement of "non-empty" naturally has two meanings: First, the empty is what is called saṃsāra; the non-empty is what is called the great nirvāṇa. Second, in contrast to the empty womb/storehouse below, it is the non-empty womb/storehouse, because within wondrous being it contains the nature's virtues.