俱舍論頌疏論本 3.13

3.13

釋曰：了自境增上者，謂六識身能了境故，眼等六根能發六識，於了自境有增上用，故眼等六總立為根。

Explanation: 'Predominant in cognizing their own objects' means that the six consciousness-bodies can cognize objects, and the six indriyas of the eye and so on can produce the six consciousnesses and have predominant function in cognizing their own objects; thus the six beginning with the eye are established altogether as indriyas.