A 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 ITeach nothing new, but instill into all men's breasts those things which the Fathers of revered memory have with harmony of statement taught... Preach nothing else than what we received from our forefathers... Accordingly, both in the rule of faith and in the observance of discipline, let the standard of antiquity be maintained throughout.
Pope Leo IThe faith of those who live their faith is a serene faith. What you long for will be given you; what you love will be yours for ever. Since it is by giving alms that everything is pure for you, you will also receive that blessing which is promised next by the Lord: the Godhead that no man has been able to see. In the inexpressible joy of this eternal vision, human nature will possess what eye has not seen or ear heard, what man's heart has never conceived.
Pope Leo IDavid's Lord was made David's Son, and from the fruit of the promised branch sprang One without fault, the two-fold nature coming together in one Person, that by one and the same conception and birth might spring our Lord Jesus Christ, in Whom was present both true Godhead for the performance of mighty works and true Manhood for the endurance of sufferings.
Pope Leo I