11 On the same day our predecessor Clement VIII joyfully communicated the news of this happy event to the world by the Apostolic constitution Magnus Dominus et laudabilis nimis . How great was the joy and goodwill with which the Roman Church welcomed the Ruthenian people on their reception into the unity of the fold may be seen also from the Apostolic Letter Benedictus sit Pastor , issued on 7th February 1596, in which the supreme pontiff informed the metropolitan and the other Ruthenian bishops of the happy establishment of the union of their whole Church with the Apostolic See. In this letter the Roman pontiff briefly set forth what had been done in the matter at Rome; he gratefully extolled the work they had by God's mercy at length undertaken, and then decreed that the legitimate uses and rites of the Ruthenian Church could be preserved inviolate. "In the same manner as the council of Florence permitted, we too permit you to retain your rites and ceremonies, which in no way injure the integrity of the Catholic faith or our union." He goes on to say that he has asked the king of Poland to extend the protection of his patronage to the bishops and all appertaining to them, and also to pay them the fullest honor and, as they desired, to admit them to the senate of the kingdom. Finally he fraternally exhorts the bishops to meet as soon as possible in a full provincial council to ratify and confirm the union of the Ruthenians with the Catholic Church.
Source: Orientales Omnes Ecclesias (Vatican.va)