瑜伽論記 3.189

3.189

補闕云：思雖發起身語二行而不發思，無明通發一切諸業，是故但說無明緣行。又三業以思為性，無明緣行則生善不善思，是故不言思緣行也。

The Supplementary Commentary says: "Although volition initiates the two formations of body and speech, it does not initiate volition; ignorance generally initiates all karmas; therefore it merely says that ignorance conditions formations. Furthermore, the three karmas have volition as their nature; when ignorance conditions formations, wholesome and unwholesome volitions are generated; for this reason it does not say that volition conditions formations."