大方廣佛華嚴經疏 53.24

53.24

Fourth, the subtle realm: that is, clarifying the ten matters of dwelling in the womb. The first one generally manifests the stages and positions; the next eight clarify manifesting the seven phases, because dwelling in the womb is the manifestor, and the youthful stage belongs to the phase of dwelling in the palace. The last one comprehensively concludes the many gates, all simultaneously manifested within a single phase, profound, secret, and difficult to know; hence it is called 'subtle'.