When the neophyte devotee accepts a pure devotee as his spiritual master, the duty of the spiritual master is to train the neophyte in the principles of regulated devotional service, or vaidhi-bhakti

Expressions researched:
"when the neophyte devotee accepts a pure devotee as his spiritual master, the duty of the spiritual master is to train the neophyte in the principles of regulated devotional service, or vaidhi-bhakti"

Narada-bhakti-sutra (sutras 1 to 8 only)

One who associates with a pure devotee of the Lord naturally accepts that person as his spiritual master, and when the neophyte devotee accepts a pure devotee as his spiritual master, the duty of the spiritual master is to train the neophyte in the principles of regulated devotional service, or vaidhi-bhakti.

Narada Bhakti Sutra 2, Purport:

The next stage in the process of elevation to love of God is sādhu-saṅga (CC Madhya 22.83), association with persons already in the highest stage of love of God. One who avoids such association and simply engages in mental speculation or so-called meditation cannot be raised to the perfectional platform. But one who associates with pure devotees or an elevated devotional society goes to the next stage—bhajana-kriyā, or acceptance of the regulative principles of worshiping the Supreme Lord. One who associates with a pure devotee of the Lord naturally accepts that person as his spiritual master, and when the neophyte devotee accepts a pure devotee as his spiritual master, the duty of the spiritual master is to train the neophyte in the principles of regulated devotional service, or vaidhi-bhakti. At this stage the devotee's service is based on his capacity to serve the Lord. The expert spiritual master engages his followers in work that will gradually develop their consciousness of service to the Lord. Therefore the preliminary stage of understanding prema, love of God, is to approach a proper pure devotee, accept him as one's spiritual master, and execute regulated devotional service under his guidance.