slip of the pen

"Just a slip of the pen, my dear."

From Time Magazine Archive

“When I wrote I called you ‘Miss Wilder’; that was a slip of the pen too.

From Jerry Junior by Orson Lowell

‘That was a slip of the pen; I hope you will excuse it.’

From Jerry by Jean Webster

And, note, last of all, about this matter, the singular grammatical irregularity in my text, which is something much more than a mere blunder or slip of the pen.

From Expositions of Holy Scripture Second Corinthians, Galatians, and Philippians Chapters I to End. Colossians, Thessalonians, and First Timothy. by Alexander Maclaren

Dear Saint Nicholas: Will you give me room to rectify a slip of the pen?

From St. Nicholas Magazine for Boys and Girls, Vol. 5, July 1878, No. 9 by Mary Mapes Dodge