Īśāvāsyopaniṣat 03
asuryā nāma te lokā andhena tamasā'vr̥tāḥ। tān te pretyābhigacchanti ye ke cātmahano janāḥ ॥3॥
Those worlds named 'Asura', i.e. demoniacal, are enveloped in the darkness of ignorance. Those killers of the self (i.e. those who do not take authentic honest actions), attain them after death.
Īśā.Bhāshya 03
'Asurya' - having the nature to delight in that which is contrary to good. Also, it is opposite of 'sura', i.e. gods. Thus it means those who turn away from lord Hari.
suṣṭhu ramaṇaviruddhatvāt asurāṇāṁ prāpyatvācca asuryāḥ।
Those who delight in that which is contrary to good are demons. Having such a nature is 'asuryā', i.e. demoniacal.
"na ca ramantyaho asadupāsanayā ātmahana"
"Indeed, they are not happy. They worship the non existent, promote nihilism, and are killers of the self."
ityuktatvāt।
- because it is stated thus in the testimonial (Bhagavata Purana).
"mahāduḥkhaikahetutvāt prāpyatvādasuraistathā। asuryā nāma te lokā tānyānti vimukhā harau॥"
"The demons acquire them (the demoniacal worlds), as they are the sole cause of the intense suffering. Those worlds are called 'Asurya', i.e. opposed to 'sura' i.e. gods, as those who turn away from lord Hari attain them."
iti vāmane।
- thus stated in the Vāmana Purāna.
ye ke ceti niyama uktaḥ।
By stating 'ye ke' , i.e. 'those who', the governing principle is conveyed (i.e. those opposed to the lord mandatorily attain darkness).
"niyamena tamo yānti sarve'pi vimukhā harau।"
"By the governing principle, all those turned away from Hari attain darkness."
iti ca ॥3॥
- there are such testimonials as well.
