ईशावास्योपनिषत् ३ – असुर्या नाम ते लोकाः
असुर्या नाम ते लोका अन्धेन तमसाऽऽवृताः।
ताꣳस्ते प्रेत्याभिगच्छन्ति ये के चात्महनो जनाः॥३॥
इदानीमज्ञानां निन्दाऽनेन मन्त्रेण क्रियते –
असुर्याः सुष्ठु रमन्ते इति सुरा आत्मारामा विद्वांसस्तेभ्योऽन्येऽसुरास्तेषां योग्याः नाम प्रसिद्धाः ते, ये लोकाः कर्मफलभूताः श्वसूकरादिदेहविशेषाः, ईश्वरापेक्षयाऽज्ञदेवा अप्यसुरा एव, अन्धेन आवरकेण तमसा स्वरूपाज्ञानेन आवृताः आच्छादिताः। तान् उक्तासुर्य्यलोकान् ते आत्मज्ञानशून्याः जनाः संसारचक्रे पुनः पुनः प्रादुर्भाववन्तः प्रेत्य शरीरं त्यक्त्वा अभिगच्छन्ति सर्वतः प्राप्नुवन्ति। ते इति तच्छब्दार्थमाह – य इति। ये के च ये केऽप्यज्ञाः आत्महनः आत्मानमजरामरलक्षणमप्यज्ञानेन जरामरणादिमन्तमिव मन्यमानाः॥३॥
Now, this mantra censures the ajñānins (ignorant ones):
The term asuryāḥ implies realms suitable for asuras, in contrast to suras—those who delight in the Self (ātmārāmaḥ) and are vidvāns (wise).
These lokas (worlds), known as asuryāḥ, are the results of karma (karma-phala-bhūtāḥ) and take the form of particular embodiments like those of pigs, dogs, etc.
Even ajña-devatās (unwise deities), in the absence of knowledge of Īśvara, are classed among asuras.
These worlds are āvṛtāḥ (covered) by andha-tamas—that is, obstructive darkness, the ignorance of one’s own svarūpa (true nature).
Those janāḥ (people) who are devoid of ātma-jñāna (knowledge of the Self) repeatedly take embodiment in saṁsāra (the cycle of rebirth) and, pretya (upon death), abhigacchanti—they reach, attain—these asurya-lokas.
The word te is explained by the pronoun ye: ye ke ca—whoever they may be—ātmahanāḥ, slayers of the Self, meaning those who, being deluded by ignorance, regard the Self—which is birthless, deathless, and undecaying—as though it were subject to birth, decay, and death.