成唯識論述記 2.383

2.383

述曰：既有同類親因緣體，餘緣亦合，即已得生，故執生等便為無用。既有水、種，復待餘生，如是橫執，實為無用。

The Commentary states: Since the substance of the direct cause and condition of the same class already exists, and the other conditions are also conjoined, it is already able to be born; therefore positing birth and the others would then be useless. Since there are already water and seed, to depend further on an extra 'birth'—such an arbitrary posits is truly useless.