俱舍論頌疏論本 7.50

7.50

學從四生五者，謂有學心從四心生，能生五心。從四心生者，謂三界善及與學心。能生五者，於前四上加無學一。

"Learner arises from four and gives rise to five": this means that the mind of a learner arises from four minds and can give rise to five minds. Arising from four minds means the wholesome of the three realms and the mind of the learner. Being able to give rise to five means adding the one of the non-learner to the preceding four.