# If the house is worthy

"If the people in that house receive you well" or "If the people who live in that house treat you well" 

# let your peace come upon it

"let them receive your peace" or "let them receive the peace that you greeted them with"

# if it is not worthy

"if they do not receive you well" or "if they do not treat you well"

# let your peace return to you

"take back your greeting of peace"