俱舍論記 7.108

7.108

「次說無漏至及學無學」者，此明二無漏心相生必從學心生無學心故。學心生無學心，必無從無學心退起學心，故無無學心生學心。

Regarding "Next, explaining the uncontaminated ... and the trainee and non-trainee": this explains that the mutual arising of the two uncontaminated minds must proceed from the mind of the trainee producing the mind of the non-trainee. The trainee's mind produces the non-trainee's mind; there is never a falling back from the non-trainee's mind to produce the trainee's mind, so the non-trainee's mind does not produce the trainee's mind.