In Caitanya-caritāmṛta ( Madhya 24.109) it is said:

bhakti vinā kevala jñāne ‘mukti’ nāhi haya bhakti sādhana kare yei ‘prāpta-brahma-laya’

Impersonalists do not take to devotional service, but take to other practices, such as the analytical study of the material elements, the discrimination between matter and spirit, and the mystic yoga system. These are beneficial only insofar as they are complementary to devotional service. Caitanya Mahāprabhu therefore told Sanātana Gosvāmī that without a touch of devotional service jñāna, yoga and Sāṅkhya philosophy cannot give one the desired results. The impersonalists wish to merge into the Supreme Brahman; however, merging into the Supreme Brahman also requires a touch of devotional service. The Absolute Truth is realized in three phases: impersonal Brahman, Paramātmā and the Supreme Personality of Godhead. All these require a touch of devotional service. Sometimes it is actually seen that these Māyāvādīs also chant the Hare Kṛṣṇa mahā-mantra, although their motive is to merge into the Brahman effulgence of the Absolute. The yogīs also at times take to chanting the Hare Kṛṣṇa mahā-mantra, but their purpose is different from that of the bhaktas. In all processes — karma, jñāna or yoga — bhakti is required. That is the purport of this verse.