8 Joined to this zeal in retaining and defending the Faith there was in Dominic a supreme reverence for the Apostolic See. It is recorded that, prostrate at the feet of Innocent III, he vowed himself to the defense of the Roman Pontificate, and that the same predecessor of ours the following night saw him in vision sustain on his courageous shoulder the tottering pile of the Lateran Basilica. History tells, too, how when he was training his first followers to Christian perfection, Dominic thought of gathering from pious and devout lay people a certain sacred militia which would defend the rights of the Church and resist heresy with vigor. Hence arose the Third Order of the Dominicans which, spreading among lay people the institute of a more perfect life, was to be a truly great ornament and defense to the Church.
Source: Fausto Appetente Die (Vatican.va)