President Biden's great-great-grandfather received a pardon from President Lincoln, according to newly discovered documents in the National Archives.

Biden's relative in the incident, Moses J. Robinette, got into a fight with another Union Army civilian employee while camped along the Rappahannock River near Beverly Ford, Virginia, as the Civil War raged on March 12, 1864, according to documents reviewed by The Washington Post.

The fight left the other man, John J. Alexander, bleeding from knife wounds, and Robinette was charged with attempted murder and was incarcerated near Florida.

Three of Robinette's friends were officers in the U.S. Army, and they petitioned Lincoln directly to overturn the sentence.

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They argued Robinette's sentence was overly harsh for "defending himself and cutting with a Penknife a Teamster much his superior in strength and size, all under the impulse of the excitement of the moment," according to the Post.

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They went on to say that Robinette was a true and faithful supporter of the Union and had opposed "traitors and their schemes to destroy the government."

"Think of his motherless Daughters and sons at home! … [Praying for] your interposition in behalf of the unfortunate Father … and distressed family of loved Children, Union Daughters & Union Sons," they added.

The petition first arrived at the desk of West Virginia Sen. Waitman T. Willey, who endorsed it and sent the request along to the White House. After a presidential review of the case, Lincoln agreed with the request and pardoned Robinette.

"Pardon for unexecuted part of punishment. A. Lincoln. Sep. 1. 1864," Lincoln wrote at the time, according to the Post. Robinette went on to live until 1903.

The White House did not immediately respond to questions from Fox News Digital regarding whether Biden was aware of this incident in his family history.