Preheat oven to 325 degrees . In a small bowl combine brown sugar, garlic, and cumin. Score ham by making diagonal cuts in a diamond pattern. Using your fingers, rub ham evenly with the sugar mixture. Place ham on a rack in a shallow roasting pan. Insert an oven-going meat thermometer into center of ham. The thermometer should not touch bone.
Bake for 1-1/2 to 2-1/4 hours or until thermometer registers 140 degrees F. If needed to avoid overbrowning, cover ham loosely with foil during the last 30 minutes of cooking time.
For sauce, in a small bowl stir together mustard, cider, and maple syrup. Season to taste with salt and pepper. If desired, serve with apple slices and garnish with sage leaves. Pass sauce with ham.