SB 1.1.15

yat-pāda-saṁśrayāḥ sūta
 munayaḥ praśamāyanāḥ
sadyaḥ punanty upaspṛṣṭāḥ
 svardhuny-āpo ’nusevayā
Synonyms: 
yat — whose; pāda — lotus feet; saṁśrayāḥ — those who have taken shelter of; sūta — O Sūta Gosvāmī; munayaḥ — great sages; praśamāyanāḥ — absorbed in devotion to the Supreme; sadyaḥ — at once; punanti — sanctify; upaspṛṣṭāḥ — simply by association; svardhunī — of the sacred Ganges; āpaḥ — water; anusevayā — bringing into use.
Translation: 
O Sūta, those great sages who have completely taken shelter of the lotus feet of the Lord can at once sanctify those who come in touch with them, whereas the waters of the Ganges can sanctify only after prolonged use.
Purport: 

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. In Bhagavad-gītā it is said that any person, regardless of birth as śūdra, woman, or merchant, can take shelter of the lotus feet of the Lord and by so doing can return to Godhead. To take shelter of the lotus feet of the Lord means to take shelter of the pure devotees. The pure devotees whose only business is serving are honored by the names Prabhupāda and Viṣṇupāda, which indicate such devotees to be representatives of the lotus feet of the Lord. Anyone, therefore, who takes shelter of the lotus feet of a pure devotee by accepting the pure devotee as his spiritual master can be at once purified. Such devotees of the Lord are honored equally with the Lord because they are engaged in the most confidential service of the Lord, for they deliver out of the material world the fallen souls whom the Lord wants to return home, back to Godhead. Such pure devotees are better known as vice-lords according to revealed scriptures. The sincere disciple of the pure devotee considers the spiritual master equal to the Lord, but always considers himself to be a humble servant of the servant of the Lord. This is the pure devotional path.