Sandilya says it is the unbroken feeling of the Universal Self in one's own self.
Hinduism
Narada Bhakti Sutra, Aphorism 18
Source Nârada, Bhakti-Sûtras (« Nârada Sûtra : An Inquiry into Love »), trad. E. T. Sturdy, 1896, archive.org · Contents