Sayyiduna Aws bin Abdullah bin Hajar al-Aslami (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) passed by me, and with him was Sayyiduna Abu Bakr (may Allah be pleased with him). This was at Khadhawat, between al-Juhfah and Harsha, and the two of them were riding a single camel, heading towards Madinah. So he (Aws) mounted them on the stallion of his camels, Ibn al-Rida', and sent with them a slave of his called Mas'ud, and said to him: Take them through the narrow passes of the roads that you know, and do not leave them until they have fulfilled their need of you and of your camel. So he took them through Thaniyyat al-Zamha', then through Thaniyyat al-Kubah, then turned with them towards the settlements, then took them through Thaniyyat al-Murrah, then brought them by way of Shu'bat Dhat Kashat, then took them through al-Mudlijah, then through al-Ishalah, then (again) through Thaniyyat al-Murrah, then brought them into Madinah, and the two of them had fulfilled their need of him and of his camel. Then the Messenger of Allah (peace and blessings be upon him) sent Mas'ud back to his master, Aws bin Abdullah. He was a simple, guileless man who did not brand his camels, so the Messenger of Allah (peace and blessings be upon him) ordered him to tell Aws to brand them on their necks with a "qayd al-faras" (a mark like a horse's hobble). Sakhr bin Malik (may Allah have mercy on him) said: "By Allah! That is our mark to this day, and 'qayd al-faras', in my view, is making two rings and drawing a line between them."
Hadith Referenceالمعجم الكبير للطبراني / باب الألف / 607