In the legal sense, this is the exclusion of an office/ministry (VII) from combination with another office or profession. The intention of incompatibility is to ensure an exercise of office that is appropriate to the task. The leading ideas to be emphasized include: the separation of powers in state law and the protection of the preaching task of the pastoral office in church law.
H.H. Klein, “Status des Abgeordneten,” in: J. Isensee & P. Kirchhof, eds., Handbuch des Staatsrechts der Bundesrepublik Deutschland, vol. III, 32005, §51, 26–30