From Henry IV, the first part, one of my favorite plays.
“Give you a reason on compulsion! If reasons were as plentiful as blackberries, I would give no man a reason upon compulsion, I.” (II.4.227–231)
Maybe? This is the only thing I could think of. It’s spoken, kind of ironically, by Falstaff, someone who lies all the time.
Edit: And this, more explicitly, from King John:
When workmen strive to do better than well,
They do confound their skill in covetousness;
And oftentimes excusing of a fault
Doth make the fault the worse by the excuse,
As patches set upon a little breach
Discredit more in hiding of the fault
Than did the fault before it was so patch’d.
(IV.2)
Spoken by Pembroke.