From The History Of the Late Rebellion: With Original Papers, And The Characters ... by Robert Patten, 1717, p. 24:
Edited to add:
...A warrant for Mr. Forster’s apprehension having been sent forth, he was, like Lord Derwentwater, obliged to fly from place to place, until he arrived at the house of Mr. Fenwick, at Bywell. Lord Derwentwater, meantime, had been secreted under the roof of a man named Lambert, in a cottage, where he had remained in safety. His horses had been seized by one of the neighbouring magistrates, and had been detained in custody for several weeks, pursuant to an order in council; yet, when he had need of them they were returned. “I afterwards asked that lord,” Mr. Batten relates, “how he came so quietly by his horses from the justice’s possession, whom the believing neighbourhood esteemed a most rigid Whig. I was answered thus, by that lord’s repeating a saying of Oliver Cromwell’s, ‘ that he could gain his ends with an ass load of gold,’ and left me to make the application."…
Oliver Cromwell (25 April 1599 – 3 September 1658)
James Radclyffe, 3rd Earl of Derwentwater (26 June 1689 – 24 February 1716)
(both above dates via wikipedia)
If Cromwell indeed said it, one should be able to place it at least by 1658.