Islam is not a race. It's a cancer that afflicts the human mind and destroys its soul. Which heaven or paradise do you think you will go when you believe this type of man is your prophet?
The earliest biography (sirat) of Muhammad's life is the work of Ibn Ishaq (85-151 A.H.) who was born in Medina. In this we learn of Muhammad's actions after he had conquered the towns of Khaybar. This event is also accepted and recorded by Ibn Kathir [1].
Kinana b. al-Rabi`, who had the custody of the treasure of B. al-Nadir, was brought to the apostle who asked him about it. He denied that he knew where it was. A Jew came (T. was brought) to the apostle and said that he had seen Kinana going round a certain ruin every morning early. When the apostle said to Kinana, "Do you know that if we find you have it I shall kill you?" he said Yes. The apostle gave orders that the ruin was to be excavated and some of the treasure was found. When he asked him about the rest he refused to produce it, so the apostle gave orders to al-Zubayr b. al-`Awwam, "Torture him until you extract what he has," so he kindled a fire with flint and steel on his chest until he was nearly dead. Then the apostle delivered him to Muhammad b. Maslama and he struck off his head, in revenge for his brother Mahmud. (Ibn Ishaq, Sirat Rasul Allah, translated as, The Life of Muhammad, (tr. A. Guillaume), Karachi: Oxford University Press, 1998, p. 515.)