俱舍論疏 28.39

28.39

The Śāstra says: "This reason is unproven, because [we] accept that there is material form." This is an objection by the Mahāsāṃghika, Mahīśāsaka, and others: You state that because they lack material form, they are generally named 'formless.' The reason of 'lacking material form' is not accepted by our school, because we accept that there is material form; thus it incurs the fault of being unproven (asiddha).