The enquired incident is reported in many authentic books of Ahadith
There were eight people who pretended to accept Islam when they fell ill in
Madina Munawwara, Rasulullah(Sallallaahu Alayhi Wasallam) advised them to
live in the outskirts of Madina Munawwara and drink the milk and urine of
camels as a means of cure. After being cured they brutally killed the
shepard and drove the camels along with them. The punishment was in lieu of
the crime committed by these murderers as well as to set an example to
others in particular the Jews who used to stay on the outskirts of Medina
Munawwara and were arch enemies of the Muslims.
And Allah Ta`ala Knows Best.
Mufti Ebrahim Desai