[Kardama Muni] looked healthy because he had directly received the nectarean sound vibrations from the lotus lips of the Personality of Godhead. Similarly, one who hears the transcendental sound vibration Hare Krsna also improves in health. We have actually seen that many brahmacaris and grhasthas connected with the International Society for Krishna Consciousness have improved in health, and a luster has come to their faces. The comparison of the sage to an unpolished gem is very appropriate. Even if a gem just taken from a mine looks unpolished, the luster of the gem cannot be stopped. Similarly, although Kardama was not properly dressed and his bodywas not properly cleansed, his overall appearance was gemlike.
From Srila Prabhupada’s purport to SB 3.21.45–47