... the Apostle says, 'he that says he abides in Christ ought himself also to walk as He walked' (I Jn. 2:6). Otherwise we make a vain pretence and show, if we follow not His steps, Whose name we glory in, and assuredly they would not be irksome to us, but would free us from all dangers, if we loved nothing but what He commanded us to love.
Pope Leo II have neither permitted, nor shall I permit, the things which have been settled by the holy fathers to be violated by any innovation.
Pope Leo IA great safeguard is the entire faith, the true faith, in which neither anything whatever can be added by anyone nor anything taken away; for, unless faith be one, it is not the faith.
Pope Leo I