俱舍論頌疏論本 1.154

1.154

生門者，是處義也。謂六根六境是心、心所生長門處，由六識生，必託根境方能起故。論云：「是能生長彼作用義（依薩婆多宗，法體先有，不可言生，但生其用耳）。」

'Gateway of arising' is the meaning of āyatana. Namely, the six faculties and six objects are the gateways and places where mind and mental factors arise and grow, because the arising of the six consciousnesses must depend on faculty and object to be able to occur. The treatise says: 'It has the meaning of being able to generate and increase their activity (according to the Sarvāstivāda school, the entity of a dharma exists beforehand and cannot be said to arise; it is only its activity that arises).'