俱舍論記 6.195

6.195

「若無為法至應緣無境」者，說一切有部難。若無為法，其體唯無。虛空、涅槃，能緣之識應緣無境而得生心。

On "If unconditioned dharmas [up to] would have to take a non-existent object": the Sarvāstivādin objects. If the entity of unconditioned dharmas is merely non-existent, then the consciousnesses that take space and nirvāṇa as their objects would have to generate mind by taking a non-existent object.