Acquisition of spiritual virtues and powers.

… the core of religious faith is that mystic feeling that unites man with God. This state of spiritual communion can be brought about and maintained by means of meditation and prayer. And this is the reason why Bahá'u'lláh has so much stressed the importance of worship. It is not sufficient for a believer to merely accept and observe the teachings. He should, in addition, cultivate the sense of spirituality, which he can acquire chiefly by the means of prayer. The Bahá'í Faith, like all other Divine religions, is thus fundamentally mystic in character. Its chief goal is the development of the individual and society, through the acquisition of spiritual virtues and powers. It is the soul of man that has first to be fed. And this spiritual nourishment prayer can best provide. Laws and institutions, as viewed by Bahá'u'lláh, can become really effective only when our inner spiritual life has been perfected and transformed. Otherwise religion will degenerate into a mere organization, and become a dead thing.
From a letter dated 8 December 1935 written on behalf of Shoghi Effendi