17.3 'Sattva' means internal organ (i.e., mind). The faith of everyone is according to his internal organ. The meaning is that with whatever Guna his internal organ is conjoined, one's faith corresponds to that Guna (i.e., Guna as object). The term Sattva covers here body, senses etc., already mentioned. Man consists of faith, viz., is the product of his faith. Of whatever faith he is, viz., with whatever faith a man is possessed, that verily he is; he is a transformation of faith of that nature. The purport is this:  If the person is associated with faith in auspicious acts he becomes associated with fruit of these auspicious acts. Conseently, attainment chiefly follows one's faith.

Sri Krsna further explains the same subject: