THE COVENANT
Covenant (Pers., Arab. `ahd, mítháq) The spiritual contract binding God and humanity. The Bahá'í Faith recognizes two covenants: first, the greater covenant, between God, represented by the Manifestation of God (q.v.), on the one hand, and humanity on the other, in which God promises to continue to send guidance to humankind, while humanity, on its part, promises to obey and follow these teachings when they come. Part of this greater covenant is the obligation which each Manifestation of God places upon his followers to accept the next Manifestation. Second, the lesser covenant, which obliges individual Bahá'ís to accept the leadership of Bahá'u'lláh's appointed successors and the administrative institutions of the Faith. Firmness in the covenant is one of the chief Bahá'í religious virtues and includes not just acceptance of the legitimacy of the Bahá'í institution but much more general attitudes of loyalty and whole-hearted commitment to the Bahá'í Faith and Bahá'í community. Challenging the authority of the center of the Bahá'í Faith is the most serious spiritual offence that a Bahá'í can commit. It called Covenant-Breaking and is considered to be a spiritual disease and is punished by expulsion from the community.
see Moojan Momen's article on Covenant, http://www.northill.demon.co.uk/relstud/covenant.htm#3.%20The%20Lesser%20Covenant [physical archive stored in /baha'i papers/history/covenant]