United States v. Wilson, 32 U.S. (7 Pet.) 150 (1833)
The decision was that if the prisoner does not accept the pardon, it is not in effect: “A pardon is a deed, to the validity of which delivery is essential, and delivery is not complete without acceptance.
https://en.m.wikipedia.org/wiki/United_States_v._Wilson
Well then, pardon me, and I will accept.