This is the definition of the American-English phrase don’t hurry, Hopkins! in Vol. III.—Fla. to Hyps. of Slang and its Analogues Past and Present ([London]: Printed for subscribers only – 1893), by John Stephen Farmer (1854-1916) and William Ernest Henley (1849-1903):

Ironical to persons slow to move or to meet an obligation.

The earliest occurrence of don’t hurry, Hopkins! that I have found is accompanied by an explanation of its origin—written from Philadelphia by a person signing themself ‘Uneda’, this note was published in Notes and Queries (London: Bell & Daldy) of 13^th March 1858:

“Don’t Hurry, Hopkins!”—This is a Kentucky expression applied to persons, I believe, who show a dilatory spirit in matters of business. It originated from the case of one Hopkins, who, having given one of his creditors a promissory note in regular form, added to it this extraordinary memorandum: “It is expressly agreed that the said Hopkins is not to be hurried in paying the above note.”

Uneda’s piece prompted one Vryan Rheged to contrast the American-English phrase with a British-English proverb in a remark published in Notes and Queries of 3^rd April 1858:

“Don’t hurry, Hopkins!” […]—Hopkins of Kentucky appears to take things leisurely. His namesake (Cisatlantic) was otherwise disposed, or whence the proverb—“as hasty as Hopkins, who went to jail overnight, and was hung next morning?”

The British physician Thomas Fuller (1654-1734) had recorded this proverb in Gnomologia: Adagies and Proverbs; Wise Sentences and Witty Sayings, Ancient and Modern, Foreign and British (London: Printed for B. Barker; and A. Bettesworth and C. Hitch, 1732):

As hasty as Hopkins, that came to Jail over-night, and was hang’d the next Morning.

Oddly enough, with the exception of one actual use of don’t hurry, Hopkins!, all the texts in which the phrase occurs merely discuss its meaning and origin. The following for example is from Volume Two: E to L of The Reader’s Encyclopedia: An Encyclopedia of World Literature and the Arts (New York: Thomas Y. Crowell Company, 1948), edited by William Rose Benét (1886-1950):

Hopkins, don’t hurry. A satirical reproof to those who are not prompt in their payments. It is said that one Hopkins, of Kentucky, gave a creditor a promissory note on which was this memorandum, “The said Hopkins is not to be hurried in paying the above.”

The only text that I have found containing an actual use of don’t hurry, Hopkins! is The Barber who Reigned for a Day, an unsigned short story first published in the Burlington Free Press & Times (Burlington, Vermont) of 20^th August 1881—and the phrase, instead of being used by antiphrasis for hurry up!, actually means not so fast!:

One good thing for the potentate, he had the Koran by heart, and pleased the priests to the core by his learning and devotion. His air was worthy the Padishah himself, as he returned to the palace from the mosque in quite a regal attitude.
A Jew family was at the gates waiting to be ransomed. It appeared that the father had ridden in at the city portals without alighting, an act of sore disrespect to the townsfolk in general, and their Dey in particular. The janissaries had offered the Jew his choice between paying five hundred douros, or being paid as many blows on the sole with the stick. The Dey shook his finger at the executioner.
“Don’t hurry, Hopkins,” cried he; “we must punish these rogues more subtly. I have it. You were in haste to greet your family, were you, you aged rascal? Then next time they shall all be at the gate, little and great, to receive you, or woe to you all! Be off! Is it not written in the book that who so pardons opens a door of heaven?”
The Hebrews crept away thankfully; but the soldiery grumbled in unison with the bastinadoist’s keynote.