The Bull of Union with the Copts was promulgated by Pope Eugene IV at the Ecumenical Council of Florence on 4 February 1442. It was part of an attempt by the Catholic Church to reunite with other Christian groups including the Coptic Church of Egypt. The attempted union with the Copts failed.
The Bull of Union with the Copts denounced Christians who continued to observe the practices of circumcision, the Jewish sabbath and "other legal prescriptions as strangers to the faith of Christ" as practiced by the Copts.
References
Bull of Union with the Copts Wikipedia(Text) CC BY-SA