俱舍論記 28.13

28.13

「別法令心至非體即心」者，說一切有部釋。別有心所，令彼心王於一境轉，名三摩地，非體即心。

"A distinct dharma causes the mind… its entity is not simply the mind": this is the explanation of the Sarvāstivāda. A separate mental factor causes that primary mind to operate upon a single object; this is called samādhi, and its entity is not simply the mind.