It's wrong to use your neighbor's stuff without their permission.
Mitchell's getting ready to go to the garage to get his mower when he notices his neighbors mower is already outside on the lawn.
Mitchell wants to decide which mower to use.
Mitchell decides to walk an extra ten feet and get his own mower from his garage.
Mitchell decides to use the neighbor's mower since it's right there, and he won't be long.
The neighbor comes outside and sees Mitchell mowing, so he says hi and gives him a wave.
The neighbor comes out to see Mitchell using his mower and is upset that Mitchell would just assume he can borrow  it.