22 The success of every society of men, for whatever purpose it is formed, is bound up with the harmony of the members in the interests of the common cause. Hence We must devote Our earnest endeavours to appease dissension and strife, of whatever character, amongst Catholics, and to prevent new dissensions arising, so that there may be unity of ideas and of action amongst all. The enemies of God and of the Church are perfectly well aware that any internal quarrel amongst Catholics is a real victory for them. Hence it is their usual practice when they see Catholics strongly united, to endeavour by cleverly sowing the seeds of discord, to break up that union. And would that the result had not frequently justified their hopes, to the great detriment of the interests of religion! Hence, therefore, whenever legitimate authority has once given a clear command, let no one transgress that command, because it does not happen to commend itself to him; but let each one subject his own opinion to the authority of him who is his superior, and obey him as a matter of conscience. Again, let no private individual, whether in books or in the press, or in public speeches, take upon himself the position of an authoritative teacher in the Church. All know to whom the teaching authority of the Church has been given by God: he, then, possesses a perfect right to speak as he wishes and when he thinks it opportune. The duty of others is to hearken to him reverently when he speaks and to carry out what he says.
Source: Ad Beatissimi Apostolorum (Vatican.va)