俱舍論記 9.184

9.184

「謂未來世至亦說至緣」者，經部答，或說一切有部答。言經部答者，於未來世法正起位未名為有，無間必有可說為起，即於起位名至緣時，故於爾時無別作者。問：向者難他未來無體而無有起，經部未來亦無有體，如何自說未來有起？解云：以聲論執定有作者方有作用，先至於緣後方正起，如是二用必有所依，故彼未來無容起義。經部意說本無作者假說作用，故未來位說起至緣，於將有位假建立故。言說一切有部答，釋文可知，無勞異解。

Regarding "namely, in the future ... it is also said to approach conditions": the Sautrāntika answers, or the Sarvāstivāda answers. To explain it as the Sautrāntika answer: at the stage when a dharma is just about to arise in the future, it is not yet called existent; because it will immediately and inevitably exist, it can be spoken of as "originating", and the very stage of origination is termed the time of approaching conditions; hence at that time there is no separate agent. Question: earlier you objected against the other that the future lacks substance and therefore has no origination; since the Sautrāntika also holds that the future lacks substance, how do they themselves say that there is origination in the future? Explanation: because the grammarian insists that there must be an agent for there to be an action—first approaching conditions and only thereafter properly originating—such two actions must have a basis, and therefore for them origination cannot reasonably occur in the future. The Sautrāntika means that there is fundamentally no agent and action is metaphorically posited; therefore, in the future stage origination and approaching conditions are spoken of, because they are metaphorically established in the stage of being about to exist. As for explaining it as the Sarvāstivāda answer, the explanation of the text is clear and requires no different interpretation.