But Abu Bakr defended Khalid, and said that he had simply made "an error of judgment and how can I punish the one whose sword is praised by Allah"   The eminent historian of Islam John Bagot Glubb writes that "Abu Bakr sent Khalid b. Waleed into Nejd with 4000 men. Many clans of Banu Taghlib hastened to visit Khalid but the Banu Yarbu' branch of the tribe, under its chief, Malik ibn Nuweira, hung back. Malik was a chief of some distinction, a warrior, noted for his generosity and a famous poet. Bravery, generosity and poetry were the three qualities most admired among the Arabs. Unwilling perhaps to demean himself by bowing to Khalid, he ordered his followers to scatter and he himself moved away across the desert alone with his family. Abu Bakr had given orders that the test to be applied to suspected rebels was that they be asked to repeat the Muslim formula and that they answer the call to prayer. Khalid, however, preferred more aggressive methods and sent out parties of horsemen to round up the fugitives and plunder their property. One such party seized Malik ibn Nuweira and his family and brought them in to Khalid, although they claimed to be Muslims. The men of Medina who were with the army protested vigorously against Khalid's ruthlessness, but without avail. The prisoners were placed under guard but, during the night, Malik ibn Nuweira and his supporters were killed in cold blood. Within 24 hours Khalid had married the widow of his victim. Malik ibn Nuweira had been executed while professing to be a believer. Indeed Khalid's marriage to the beautiful Layla gave rise to the suspicion that Malik had been killed with the object of making her available to the conqueror. The men of Medina, who had already opposed Khalid's ruthless actions, were outraged by the death of Malik. A certain Abu Qatada, an erstwhile friend and companion of Muhammad, hastened to Medina to complain to Abu Bakr, who summoned Khalid to answer the accusation. Umar b. Khattab pressed the caliph to deprive Khalid of his command. Khalid, returning to Medina, claimed that he had not ordered the execution of Malik, but that his instructions to the guards had been misunderstood. The wise Abu Bakr, whatever he may have thought of the morals of his lieutenant, was aware of his prowess. ‘I will not sheathe a sword which God has drawn for His service,' he exclaimed.