The proverbial saying ‘A leopard cannot change its spots’ expresses the notion that things cannot change their innate nature. It is normally used to suggest that people who have done bad things will always be bad people.

‘A leopard cannot change its spots’ is found in the Bible, Jeremiah 13:23 (King James Version):

“Can the Ethiopian change his skin, or the leopard his spots? then may ye also do good, that are accustomed to do evil.”

The expression has been used in English since the early English versions of the Bible. However, the text doesn’t appear in Wycliffe’s 1384 bible and the earliest biblical use that I know of is in the Geneva Bible, 1560:

Can the blacke More change his skin? or the leopard his spottes?

This is pre-empted by Johan Bale’s First Examination of Anne Askew, 1546:

Their olde condycyons wyll they change, whan the blackemoreæne change hys skynne, and the catte of the mountayne [leopard] her spottes.

This is clearly almost identical to the biblical text, but which came first isn’t clear. It could be that Bale took his lead from an existing Latin bible or it could be that the Geneva bible writers copied his text.