I found numbers of letters, especially from Northerners, that threatned the safety and or life of Wise (and even his family) should the Governor go through with the execution of John Brown, but I only found one from a slave state; this one. It seems that some people felt that Brown's actions were wrong and that he should be punished, but that his deed did not warrant a capital punishment.
I found it interesting that this particular letter starts off quite respectful, but quickly turns threatening toward the governor. The writer, apparently a slaveholder, explains that he has slaves, but that he would not demand blood should they be taken from him. More than once he uses Biblical references and curses to remind Wise of the importance of his decision.
Here is the letter, edited for spelling and punctuation:
Louisville, Nov. 28, 1859
I feel I cannot rest satisfied or die happy should I fail to speak a word in behalf of those unfortunate men held at Charlestown under sentence of death.
I do not in any degree justify that insurrection at Harpers Ferry, but it does not present so sickening a picture to the conation of man as hanging coolly five human beings, and I earnestly entreat you as you regard your future happiness to commute their punishments. If you do not darkness and confusion will come over you and the vengeance of blood will forever be at your heels. I demand their release from the gallows; justice demands it and all that is sacred cries for mercy. You will never see another happy day should you persist in hanging those men. Your bed will henceforth be a bed of thorns and each day will dawn darker and darker upon you until your miserable life will end and you will never hear amidst the torments of the damned. So beware of your [illegible]. I have slaves but should they all be taken from me I should not require the blood of a fellow man. I did think you would commute their punishments, but I see by the papers that you intend on carrying out your hellish purpose; but remember, you will be a vagabond and fugitive on earth and mildew will come over your posterity.
I deeply regret that I have written at so late a day. May God in heaven influence you to act in accordance with the Gospel. He that is without sin, let him cast the first stone.