Bhagavatapurana 4.22.21

4.22.21

śāstreṣv iyān eva suniścito nṛṇāṃ kṣemasya sadhryag-vimṛśeṣu hetuḥ /
asaṅga ātma-vyatirikta ātmani dṛḍhā ratir brahmaṇi nirguṇe ca yā //

21. In sastras that constitute thoroughly reasoned enquiry, the cause or means of heavenly happiness for men is (made out to be) but this—absence of attachment to things other than Atman and (finding) constant delight in Atman who is Brahman destitute of attributes.