28 If then it is the climax of gladness and the consummation of holy joy, when that comes to pass which the Psalmist said: 'Behold how good and how pleasant it is for brethren to live together in unity' ( Ps . 132, I); if then the glory of God combined with the greatest profit for all is apparent when the sheep of Christ are joined together in the fullness of truth and the fullness of charity, let those whom with sorrow and love we have mentioned above, consider whether it is right and expedient that, principally on account of the original ambiguity of certain words, they should still hold apart from the one Holy Church, founded on sapphires (cf. Is . liv, 11), that is to say, on the Prophets and Apostles, on the supreme corner stone itself, Christ Jesus (cf. Eph . ii, 20).
Source: Sempiternus Rex Christus (Vatican.va)