俱舍論疏 5.204

5.204

論「此難不然至而不相違」，有部通也。雖體俱有，用有前後。謂生作用令未生法生至現在，現在已生豈須生相？由此生時非即是住、衰異、壞滅。

On the treatise passage: "This objection is incorrect … and there is no contradiction": the Vaibhāṣika resolves the objection. Although their essences co-exist, their functions occur in succession. Namely, the function of arising causes the unarisen phenomenon to arise into the present; once it has already arisen into the present, what need is there for the characteristic of arising? Therefore, when it arises, it is not simultaneously staying, decaying, or ceasing.