俱舍論記 13.16

13.16

「然心所思至所等起故」者，釋下兩句。論主述說一切有部三業，故置然言。思是意業，思是能作，能等起。身、語是所作，所等起。

"However, mental volition... because it is what is originated" explains the lower two lines. Because the treatise master relates the three karmas of the Sarvāstivāda, he inserts the word 'however'. Volition is mental karma; volition is that which acts, that which originates. Body and speech are what is done, what is originated.