俱舍論記 1.61

1.61

「欲令世間至如理簡擇」者，別明說意。欲令世間諸有情類得擇法故，所以說此對法。伏難云：說餘二藏足能利物，何須別說此對法耶？今通言：若離對法，弟子不能於諸法相如理簡擇，經正詮定、律正詮戒，定、戒二種於斷惑中但助非正。

On "Wishing to cause the world [...] discern in accordance with principle": this specifically explains the intention of speaking. Wishing to cause all kinds of sentient beings in the world to attain the discernment of dharmas, for this reason he spoke this Abhidharma. An implicit objection asks: Speaking the other two pitakas is sufficient to benefit beings; why was it necessary to speak this Abhidharma separately? Now it is resolved by saying: If apart from the Abhidharma, disciples cannot discern the characteristics of dharmas in accordance with principle; the sūtras primarily explain concentration, and the vinaya primarily explains moral discipline; concentration and moral discipline are merely auxiliary, not primary, in cutting off defilements.