大毘盧遮那成佛經疏 4.27

4.27

The sūtra says: "Thereafter cultivate the ground. In their proper order, it should possess all virtues." This means that whenever one wishes to create a maṇḍala, one must first perform rituals such as this, and only then dig the ground to inspect and cultivate it. It also combines the three meanings of ground and both the shallow and secret interpretations, up to possessing all branches in the order spoken by the sūtra; therefore it is said that it should possess all virtues.