CC Madhya-lila 09.032 - Padma Purana
Sri Caitanya-caritamrta
CC Madhya-lila
CC Madhya 9.32, Translation and Purport:
“(Lord Śiva addressed his wife, Durgā:) "O Varānanā, I chant the holy name of Rāma, Rāma, Rāma and thus enjoy this beautiful sound. This holy name of Rāmacandra is equal to one thousand holy names of Lord Viṣṇu."
This is a verse from the Bṛhad-viṣṇu-sahasranāma-stotra in the Uttara-khaṇḍa of the Padma Purāṇa (72.335).