Spiritual spark (CC and other books)
Sri Caitanya-caritamrta
CC Adi-lila
The poetical comparison of Lord Caitanya and Lord Nityānanda to the sun and moon is very significant. The living entities are spiritual sparks, and their constitutional position is to render devotional service to the Supreme Lord in full Kṛṣṇa consciousness. So-called pious activities and other ritualistic performances, pious or impious, as well as the desire to escape from material existence, are all considered to be coverings of these spiritual sparks. The living entities must get free from these superfluous coverings and fully engage in Kṛṣṇa consciousness. The purpose of the appearance of Lord Caitanya and Lord Nityānanda is to dispel the darkness of the soul. Before Their appearance, all these superfluous activities of the living entities were covering Kṛṣṇa consciousness, but after the appearance of these two brothers, people's hearts are becoming cleansed, and they are again becoming situated in the real position of Kṛṣṇa consciousness.