When Don Quixote saw it, rendered in such lifelike style that one would have said Christ was speaking and Paul answering, "This," he said, "was in his time the greatest enemy that the Church of God our Lord had, and the greatest champion it will ever have; a knight-errant in life, a steadfast saint in death, an untiring labourer in the Lord’s vineyard, a teacher of the Gentiles, whose school was heaven, and whose instructor and master was Jesus Christ himself."
…time; and what made me believe this was what I knew of the base and extravagant designs which our people harboured, designs of such a nature that I think it was a divine inspiration that moved his Majesty to carry out a resolution so spirited; not that we were all guilty, for some there were true and steadfast Christians; but they were so few that they could make no head against those who were not; and it was not prudent to cherish a viper in the bosom by having enemies in the house.
There are no more uses of "steadfast" in the book.
Show samples from other sources
But then, that’s who Helene is: Her faith is steadfast.
Sabaa Tahir -- An Ember in the Ashes
Moving apace with the river was a long single-file line of men, eyes aimed at their feet, shoulders tense, walking steadfastly nowhere.