SB 7.15.25
rajas tamas ca sattvena
sattvam copasamena ca
etat sarvam gurau bhaktya
puruso hy añjasa jayet
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
One must conquer the modes of passion and ignorance by developing the mode of goodness, and then one must become detached from the mode of goodness by promoting oneself to the platform of suddha-sattva. All this can be automatically done if one engages in the service of the spiritual master with faith and devotion. In this way one can conquer the influence of the modes of nature.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Just by treating the root cause of an ailment, one can conquer all bodily pains and sufferings. Similarly, if one is devoted and faithful to the spiritual master, he can conquer the influence of sattva-guna, rajo-guna and tamo-guna very easily. Yogis and jñanis practice in many ways to conquer the senses, but the bhakta immediately attains the mercy of the Supreme Personality of Godhead through the mercy of the spiritual master. Yasya prasadad bhagavat-prasado. If the spiritual master is favorably inclined, one naturally receives the mercy of the Supreme Lord, and by the mercy of the Supreme Lord one immediately becomes transcendental, conquering all the influences of sattva-guna, rajo-guna and tamo-guna within this material world. This is confirmed in Bhagavad-gita (sa gunan samatityaitan brahma-bhuyaya kalpate). If one is a pure devotee acting under the directions of the guru, one easily gets the mercy of the Supreme Lord and thus becomes immediately situated on the transcendental platform. This is explained in the next verse.