"Can the Ethiopian change his skin or the leopard his spots? Neither can you do good who are accustomed to doing evil"
This passage often set forth by Calvinists is a classic example of seeing something which is not there by reading it out of context. It is common for Calvinists to do this type of thing. The Calvinist would have you believe this passage concerns the inability of man to change his own condition and that this supports his doctrine of Total Depravity.
Firstly, no one does believe that we can change our own condition. No one believes they themselves willed their own new birth. I don't know of anyone who has claimed, "I willed myself born again!" What we do is come to God so that he himself can make us born again.
Secondly, the passage goes on to say that those who are accustomed to doing evil can do no good. But notice what else this passage says:"You have forgotten Me and have gone after false gods" (13:25).
This passage concerns the whole house of Israel and Judah and God is telling Jeremiah to prophesy to them that they need to return to Him. Notice the preceding context:
Genesis 6:5"The LORD saw that the wicknedness of man was great upon the earth and that every imagination of the thoughts of his heart was only evil continually."