俱舍論疏 13.182

13.182

論「相應善者至如雜藥水」，此釋第三相應善也。諸心、心所成善性，要由與彼慚等相應方成善故。如雜藥水亦為藥，以雜藥故。

The commentary states: "What is wholesome by association ... like water mixed with medicine." This explains the third, wholesome by association (samprayukta-kuśala). For the various minds and mental factors to become wholesome in nature, they must become wholesome by being associated with shame and so forth. Just as water mixed with medicine also becomes medicine, because it is mixed with medicine.