Pure devotees of the Lord are more powerful than the waters of the sacred river Ganges. One can derive spiritual benefit out of prolonged use of the Ganges waters. But one can be sanctified at once by the mercy of a pure devotee of the Lord.
His Divine Grace A. C. Bhaktivedanta Swami Prabhupada
Srimad-Bhagavatam 1.1.15, Purport

Devotional service to Krishna is the chief function of the living entity. There are different methods for the liberation of the conditioned soul—karma, jnana, yoga, and bhakti—but all the others are dependent on bhakti.
Sri Chaitanya Mahaprabhu
Sri Chaitanya-charitamrita, Madhya-lila 22.17.

By worship of the Lord, who is the source of all beings and who is all-pervading, a man can attain perfection through performing his own work.
Lord Sri Krishna
Bhagavad-gita 18.46

The names of Sri Krishna, or in other words the names Hare Krishna, indicate Sri Radha-Govinda, and the names Hare Rama also refer to Radha-Govinda.
Srila Bhaktisiddhanta Sarasvati Thakura
Commentary on Sri Chaitanya-bhagavata, Adi-khanda 11.67

The one Supreme Lord lives hidden inside all created things. He pervades all matter and sits within the hearts of all living beings. As the indwelling Supersoul, He supervises their material activities. Thus, while having no material qualities Himself, He is the unique witness and giver of consciousness.
Svetashvatara Upanishad 6.11

My Lord, please free me, Your partial expansion, from the bondage created by Your Maya. Please do this, O abode of supreme bliss, by directing me to the service of Your feet.
Srila Sridhara Swami
Commentary on Srimad-Bhagavatam 10.87.21

Understand this essential fact of life: life is temporary and full of all kinds of miseries. So take shelter of the holy name as your only business.
Srila Bhaktivinoda Thakura
Arunodaya-kirtana 1.6

As soon as one becomes inimical to Krishna and desires sense gratification, he is immediately struck down by the illusory energy of the Lord.
Srila Jagadananda Pandita
Prema Vivarta 2

Lord Krishna, the original Supreme Personality of Godhead, sometimes descends to the world of men with His associates and transcendental abode. He removes the burden of the earth and delights His devotees.
Sri Vishvanatha Chakravarti Thakura
Aishvarya-kadambini 2.6