Baptism is the centre of Mandaean life, and it is not a single event. The masbuta is repeated: on Sundays, at festivals, at marriage, before priestly acts, after ritual impurity, and as often as a person wishes. It must be performed in flowing natural water, which Mandaeans call yardna after the Jordan, and it therefore requires a river. That single requirement has shaped the geography of the religion, tying it to the lower Tigris, Euphrates and Karun, and it is the aspect of Mandaean practice hardest to reproduce in exile.
The rite is conducted by a priest and involves triple immersion, signing, drinking of the water, a crown of myrtle, the taking of the priest's hand, and a sacramental bread and water. A cult hut, the mandi, is built beside the water with an enclosed pool fed from the river, and the building is a shelter for the rite rather than a hall for preaching to an assembly. A white ritual garment, the rasta, is worn for baptism, for marriage and for burial.
The priesthood has three ranks: the tarmida, the ganzibra or treasurer, and above them the rish ama, head of the people, an office that has long stood vacant. Ordination is lengthy and demanding, requires descent from a priestly family in practice, and requires a ritual purity difficult to maintain in modern conditions. The result is a chronic shortage. Several diaspora communities have too few priests to serve their population, and priests travel between countries to perform rites.
Two rules make recovery from decline very hard. Mandaeism does not accept converts; one is born a Mandaean. And marriage outside the community generally means the loss of the children to it. Combined with dispersal across a dozen countries, an ageing priesthood and the loss of accessible rivers, these rules mean that the demographic decline is not easily reversible by any means available to the community itself. Mandaean organisations abroad have responded by building artificial baptismal pools fed with flowing water and by teaching Mandaic to children born outside the region.