Final answer:
The Third Amendment allows you to say "no" if a soldier wants to stay in your house.
Step-by-step explanation:
The amendment that allows you to say "no" if a soldier wants to come and stay in your house is the Third Amendment.
The Third Amendment to the United States Constitution states that no soldier shall, in a time of peace, be quartered in any house without the consent of the owner.
This means that as a homeowner, you have the right to refuse to allow a soldier to stay in your house unless you provide your consent.
Learn more about Third Amendment, soldier quartering