俱舍論頌疏論本 4.101

4.101

釋曰：非得淨無記者，三性門也。謂非得性無覆無記，淨謂無覆也。

Explanation: "Non-possession is pure indeterminate" is the section on the three natures. Non-possession by its nature is non-defiled indeterminate; "pure" means non-defiled.