Some thieves killed the Prophet’s (p) herdsman, and hence he sent out his Companions in puruit of these criminals to be brought to justice.
“THE EXPEDITION OF DHU QARAD
…We returned to Medina with the Messenger of God – that is, after the peace of al-Hudaybiyah. The Messenger of God sent out his camels with Rabah, and I went out with him with a horse belonging to Talhah b. Ubaydallah. When we woke up in the morning, we saw that Abd al-Rahman b. Uyaynah had raided the camels of the Messenger of God, driving off all of them and killing their herdsman.
I said: ‘Rabah, take this horse and get to Talhah. Tell the Messenger of God that the polytheists have raided his camels.’ Standing on a hill, I faced Medina and shouted, ‘A raid!’ three times. Then I set out after the enemy, shooting arrows at them…” 
Hajjah Amina Adil:
“Meanwhile, the unbelievers had been stirring up the tribe of Ghatafan. They had attacked the herd of the Prophet’s camels, which were pasturing on the meadows of Zikard, and captured twenty of his camels. They killed the camel herder, the son of Abu Dharr al-Ghifari, and took his wife captive. The first of the Muslims to hear this news was the marksman Aslama. He and some of his friends went after the camel robbers and showered them with heavy rain of arrows.
In this way they took the Prophet’s camels from their hands, but most of the thieves got away and fled to the valley where their commander Uyayna waited for them. Aslama returned to Madinah and said to the Prophet, ‘Oh Rasulullah! If you give me one hundred men, I will round up all the bandits and bring them here.’ The Holy Prophet replied, ‘If the enemy asks for quarter, treat them with kindness!’ Again we see how perfect is the way of Islam.” 
 The History of al-Tabari: The Victory of Islam: Muhammad at Medina, [Translator Michael Fishbein], volume 8, page 43 – 45
 Muhammad, the Messenger of Islam: His Life & Prophecy By Hajjah Amina Adil, page 437