Custom in sin.

Let the wild leopards of the wood
Put off the spots that nature gives,
Then may the wicked turn to God,
And change their tempers and their lives.

As well might Ethiopian slaves
Wash out the darkness of their skin,
The deed as well might leave their graves,
As old transgressors cease to sin.

Where vice has held its empire long,
'Twill not endure the least control;
None but a power divinely strong
Can turn the current of the soul.

Great God! I own thy power divine
That works to change this heart of mine;
I would be formed anew, and bless
The wonders of creating grace.