The ornamental design for a harness with leash, as shown and described.
FIG. 1 is a perspective view of a harness with leash with a male end of the harness removed from the female end of the leash showing my new design;
FIG. 2 is a perspective view of a harness with leash with a male end of the harness inserted into the female end of the leash;
FIG. 3 is a perspective view of a harness with leash with a male end of the harness removed from the female end of the leash; and,
FIG. 4 is a perspective view of the harness with leash with a male end of the harness inserted into the female end of the leash, and the leash flap connecting element shown detached from the central buckle.
The portions shown in broken lines are included for illustrative purpose only and form no part of the claimed design.