俱舍論記 28.94

28.94

「或應說何故至勝尋伺故」者，經部又難。或應說何故初唯立五支？汝若謂此五資初定勝立為支者。此不應理，念、慧能資初定勝尋、伺故，應立念、慧為支。

Regarding the passage "Or you should explain why... superior to investigation and scrutiny": The Sautrāntika again objects: Or you should explain why only five factors are established in the first [absorption]. If you say that because these five assist the first absorption pre-eminently they are established as factors: This is not reasonable, because mindfulness and discernment can assist the first absorption superior to investigation and scrutiny; hence mindfulness and discernment should be established as factors.