Amendment 3 is that you don't not have to house a soldier at any time.
For example, say if you and your family are living peacefully and a soldier comes to your house asking you to stay at your home.
You feel bad if you say no but, you don't want them to come and invade your private space.
If a random person comes into your house you can feel unsafe and uncomfortable in your own home.
Amendment 3 allows you to say no to housing any soldier during battle or not in battle.