The spiritual master gives us the process how to realize in perfection the Supreme Absolute Truth. One who thinks he can “bribe” the guru by his service is nothing but a joker. We should not serve the guru for material benefits.
Srila Prabhupada explains:
Great personalities of the material world are very eager to render welfare service to human society, but actually no one can render better service than one who distributes the knowledge of spiritual realization in relation with the Supreme Personality of Godhead. All living entities are within the clutches of the illusory energy. Forgetting their real identity, they hover in material existence, transmigrating from one body to another in search of a peaceful life. Since these living entities have very little knowledge of self-realization, they are not getting any relief, although they are very anxious to attain peace of mind and some substantial happiness. Saintly persons like the Kumaras, Narada, Prahlada, Janaka, Sukadeva Gosvami and Kapiladeva, as well as the followers of such authorities as the Vaisnava acaryas and their servants, can render a valuable service to humanity by disseminating knowledge of the relationship between the Supreme Personality of Godhead and the living entity. Such knowledge is the perfect benediction for humanity.
Knowledge of Krsna is such a great gift that it is impossible to repay the benefactor. Therefore Prthu Maharaja requested the Kumaras to be satisfied by their own benevolent activities in delivering souls from the clutches of maya. The king saw that there was no other way to satisfy them for their exalted activities. The word vinoda-patram can be divided into two words, vina and uda-patram, or can be understood as one word, vinoda-patram, which means "joker." A joker's activities simply arouse laughter, and a person who tries to repay the spiritual master or teacher of the transcendental message of Krsna becomes a laughingstock just like a joker because it is not possible to repay such a debt. The best friend and benefactor of all people is one who awakens humanity to its original Krsna consciousness.
SB 4.22.47 purport