tell him thanks for asking, but no,
your still working the land, deer have been pushed out because of the work, trying limit the pressure until they return.
tell him if he wants to hunt next season you can probably use some help during the summer if he's interested.

we all know the rules of etiquette for permission,
ask in advance, offer to help, dress appropriate. blah blah blah
99% of the time that doesnt happen, they come last minute asking for permission, if they ask at all.