CC Ādi 5.33

‘siddha-loka’ nāma tāra prakṛtira pāra
cit-svarūpa, tāṅhā nāhi cic-chakti vikāra
Synonyms: 
‘siddha-loka’ — the region of the Siddhas; nāma — named; tāra — of the effulgent atmosphere; prakṛtira pāra — beyond this material nature; cit-svarūpa — full of knowledge; tāṅhā — there; nāhi — there is not; cit-śakti-vikāra — change of the spiritual energy.
Translation: 
That region is called Siddhaloka, and it is beyond the material nature. Its essence is spiritual, but it does not have spiritual varieties.