The result of asking unqualified guy

A married man having 3 sons suspected that one his children is not his, i.e. he thinks that his wife made an affair with another man, so he decided to go and ask a schoolar or a priest, the answer was dear you take your wife and sons to desert or green area and you stay over night there and you must draw a circle around the area where you will all sleep, the man said ok, when you woke up, see the one who is outside the circuit is born by illegal affair.
The man said thanks and went with his family to the desert and draw a circle and they slept in the circle, the next day the man woke up and find him self outside the circle.