This is our thanks....😡

La
My husband and I live in a rental home on three acres of land. We have someone who comes once every two weeks to mow the grass. Well, it's rained here a lot the last week or so and the grass is getting really high. Our landlord is picky about the grass, too. 
My husband and I have a push mower. It takes 6 HOURS to push mow our yard. My husband's grandparents--who live 20 mins from us--have a riding mower. My husband does A LOT for them...he fixes stuff around the house for them, helps with yard work, we've cooked dinner for them several times, etc. Since the guy can't come cut our grass until next Wednesday, my hubby asked to borrow his grandfather's riding mower. 
His grandfather said he'd think about it, then calls back and very rudely tells my husband NO, he can't borrow it. He said that's the yard guys responsibility and our grass could grow until then. My hubby and I are both pretty pissed. He never asks for anything and always helps them out.
He's so hurt that he doesn't even want to talk to his grandparents right now and I'm stuck being a mediator. 😬 A decent riding mower costs 3,000-5,000 dollars and we are trying to put money towards our baby that will be joining us in January...this the reason we haven't bought our own.