大方廣佛華嚴經隨疏演義鈔 89.58

89.58

疏「界城即十八界」者，十八界是生死因相，故晉經云「三界」。三界為城郭，約果相故。言「界地即地等四界」者，《俱舍》云「大種謂四界，即地水火風。能成持等業，堅濕煖動性」故。及六處等，並如二地。

In the commentary, "The city of the dhātus means the eighteen dhātus": the eighteen dhātus are the causal marks of saṃsāra, so the Jin translation says "the three realms". The three realms serve as city walls in terms of the fruit marks. Where it says "The ground of the dhātus means the four dhātus of earth and so forth": the *Kośa* says, "The great elements are called the four dhātus, namely earth, water, fire, and wind; / capable of performing the actions of supporting and so on, with the natures of solidity, moisture, heat, and motion"; as well as the six sense-bases and so forth, all as in the second stage.