SB 4.31.12
kim va yogena sankhyena
nyasa-svadhyayayor api
kim va sreyobhir anyais ca
na yatratma-prado harih
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Transcendental practices that do not ultimately help one realize the Supreme Personality of Godhead are useless, be they mystic yoga practices, the analytical study of matter, severe austerity, the acceptance of sannyasa, or the study of Vedic literature. All these may be very important aspects of spiritual advancement, but unless one understands the Supreme Personality of Godhead, Hari, all these processes are useless.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
In Caitanya-caritamrta (Madhya 24.109) it is said:
bhakti vina kevala jñane ‘mukti’ nahi haya
bhakti sadhana kare yei ‘prapta-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 Mahaprabhu therefore told Sanatana Gosvami that without a touch of devotional service jñana, yoga and Sankhya 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, Paramatma and the Supreme Personality of Godhead. All these require a touch of devotional service. Sometimes it is actually seen that these Mayavadis also chant the Hare Krsna maha-mantra, although their motive is to merge into the Brahman effulgence of the Absolute. The yogis also at times take to chanting the Hare Krsna maha-mantra, but their purpose is different from that of the bhaktas. In all processes — karma, jñana or yoga — bhakti is required. That is the purport of this verse.