俱舍論頌疏論本 24.48

24.48

釋曰：有頂由無漏者，斷有頂染唯無漏道，非有漏道，以有漏道欣上厭下，於有頂地無上可欣，故有漏道不斷有頂。

The explanation says: 'Detachment from the peak of existence is by the uncontaminated' means that the abandonment of defilement of the peak of existence is only through the uncontaminated path, not through the contaminated path; because the contaminated path delights in what is above and is disgusted with what is below, and in the plane of the peak of existence there is nothing above to delight in, the contaminated path does not abandon the peak of existence.