This morbid meddling of conscience with an immaterial matter betokened, it is to be feared, no genuine and steadfast penitence, but something doubtful, something that might be deeply wrong beneath.
Hester Prynne, gazing steadfastly at the clergyman, felt a dreary influence come over her, but wherefore or whence she knew not, unless that he seemed so remote from her own sphere, and utterly beyond her reach.
It was strange, the way in which Pearl stood, looking so steadfastly at them through the dim medium of the forest gloom, herself, meanwhile, all glorified with a ray of sunshine, that was attracted thitherward as by a certain sympathy.
Hester’s strong, calm steadfastly-enduring spirit almost sank, at last, on beholding this dark and grim countenance of an inevitable doom, which at the moment when a passage seemed to open for the minister and herself out of their labyrinth of misery—showed itself with an unrelenting smile, right in the midst of their path.
In the little chaos of Pearl’s character there might be seen emerging and could have been from the very first—the steadfast principles of an unflinching courage—an uncontrollable will—sturdy pride, which might be disciplined into self-respect—and a bitter scorn of many things which, when examined, might be found to have the taint of falsehood in them.
"Hester Prynne," said he, leaning over the balcony and looking down steadfastly into her eyes, "thou hearest what this good man says, and seest the accountability under which I labour.
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.