菩薩瓔珞本業經 1.59

1.59

"Buddha-son! Sixth is the power of the Buddha's teaching, that is to say, the twelve bases: the six external objects reach the six internal sense faculties and serve as the places into which consciousness enters, and so they are called bases. As for contemplation with wisdom: it is not internal, not external, and not in between, because all phenomena have neither self nor other.