He now studied very hard, in order to make up for his want of preparation for his office. He was very active in all sorts of pious and charitable works, and he soon became famous as a preacher. His steady firmness in maintaining the orthodox faith was especially shown when Valentinian's widow, Justina, who was an Arian, wished to take one of the churches of Milan from the Catholics, and to give it to her own sect; and after a hard struggle, Ambrose got the better of her. He afterwards gained a very great influence both over Justina's son, Valentinian II., and over his elder brother Gratian. And when Gratian had been murdered by the friends of Maximus (the same Maximus who put Priscillian to death), and Theodosius came into the West to avenge his murder (A.D. 388), Ambrose had no less power with Theodosius than he had had with the younger emperors. Theodosius took up his abode for a time at Milan after he had defeated and slain the usurper Maximus. Soon after his arrival in the city, he went to service at the cathedral, and was going to seat himself in the part of it nearest to the altar, as at Constantinople the emperor's seat was in that part of the church. But Ambrose stopped him, and told him that none but the clergy were allowed to sit there; and he begged the emperor to take a place at the head of the people outside the altar-rails. Theodosius was so far from being angry at this, that he thanked the bishop, and explained to him how it was that he had made the mistake of going within the rails; and when he got back to Constantinople, he astonished his courtiers by ordering that his seat should be removed to a place answering to that in which he had sat at Milan; for that, he said, was much more seemly and proper.