Lucy Smith says that after Joseph repented of his sins, he was given an instrument by God by which to translate the BOM.
Lucy Mack Smith letter, Waterloo, New York to Solomon Mack, Gilsum, New Hampshire, January 6, 1831, 2, MS 3468, Church History Library
Joseph after repenting of his sins and humbling himself before God was visited by an holy Angel whose countenance was as lightning and whose garments were white above all whiteness and gave unto him commandments which inspired him from on high. and gave unto him by the means of which was before prepared that he should translate this this book, and by <reading> this this our eyes are opened that we can see the situation in which the world now stands that the eyes of the whole world are blinded, that the churches have all become corrupted, yea every church upon the face of the earth that the Gospel of Christ is no where preached. this is the situation which the world is now in, and you can judge for yourselves if we did not need something more than the wisdom of men for to show us the right way