By decree of the angels and by the command of the holy men, we excommunicate, expel, curse and damn Baruch de Espinoza, with the consent of God, Blessed be He, and with the consent of the entire holy congregation, and in front of these holy scrolls with the 613 precepts which are written therein; cursing him with the excommunication with which Joshua banned Jericho and with the curse which Elisha cursed the boys and with all the castigations which are written in the Book of the Law. Cursed be he by day and cursed be he by night; cursed be he when he lies down and cursed be he when he rises up. Cursed be he when he goes out and cursed be he when he comes in. The Lord will not spare him, but the anger of the Lord and his jealousy shall smoke against that man, and all the curses that are written in this book shall lie upon him, and the Lord shall blot out his name from under heaven. And the Lord shall separate him unto evil out of all the tribes of Israel, according to all the curses of the covenant that are written in this book of the law. But you that cleave unto the Lord your God are alive every one of you this day.
Baruch Spinoza managed to get the harshest ostracism ever pronounced on a member of the Portuguese-Jewish community in Amsterdam. The reason? Basically, he disagreed with everything the leaders of the community believed in and made them worry for their already-shaky position in a Catholic society.