俱舍論疏 6.147

6.147

論「異熟即因至業之異熟」，雙難兩釋。言「異熟生眼」者，即是異熟即因，何得說言異熟之因？言「業之異熟」者，即不得言異熟即因。

The treatise says: "Maturation is itself the cause [...] the maturation of karma." This poses objections against both explanations. When one says "the eye born of maturation," that means maturation is itself the cause; how can one say it is the cause of maturation? When one says "the maturation of karma," one cannot say that maturation is itself the cause.