Primarily, anasūyā (anasuya) is an inherent quality. Mahābhārata (Mahabharata) has equated this quality with courteousness and virtuosity.
The great affliction felt within by one at witnessing the abundance of another’s material prosperity is called asūyā (asuya). The principle of not entertaining the feeling of asūyā is defined as anasūyā—
dhanādyairadhikaṃ dṛṣṭvā bhṛśaṃ manasi tāpanam.
asūyā kīrtitā sadbhistadayoge’nasūyatā.
Jealousy, asūyā and other vices have been identified in Manusaṃhitā (Manusamhita) as vices stemming from rage. The annotator Kullūkabhaṭṭa (Kullukabhatta) has defined the word ‘asūyā‘ as finding baseless failings in others’ virtues. One who does not possess the element of asūyā is known as anasūyā.
In Vṛhannāradīyapurāṇa (Vrihannaradiyapurana) too, the reference of asūyā comes up following the context of krodha (anger). Hence, the definition of anasūyā follows that of akrodha (without anger).
[See Annotation of Kullūkabhaṭṭa (Kullukabhatta)]