The endowment of garments as a mark of favor is an ancient Middle Eastern tradition, recorded in sources such as the Hebrew Bible and Herodotus.
In the Islamic world, Muhammad himself set a precedent when he removed his cloak (burda) and gave it to Ka'b ibn Zuhayr in recognition of a poem praising him. Indeed, the term khilʿa "denotes the action of removing one's garment in order to give it to someone".
The practice of awarding robes of honour appears in the Abbasid Caliphate, where it became such a regular feature of government that ceremonies of bestowal occurred almost every day, and the members of the caliph's court became known as 'those who wear the khilʿa' (aṣḥāb al-khilʿa). The bestowal of garments became a fixed part of any investment into office, from that of a governor to the heir-apparent to the throne. As important court occasions, these events were often commemorated by poets and recorded by historians.
In Egypt in the Fatimid Caliphate, the practice spread to the wealthy upper middle classes, who began conferring robes of honor on friends and relatives, in emulation of the aristocracy. Later, under the Mamluk Sultanate, the system was standardized into a system of classes reflecting the divisions of Mameluke society, each with its own ranks: the military (arbāb al-suyūf), the civilian bureaucracy (arbāb al-aqlām), and the religious scholars (al-ʿulamāʾ).
The distribution of the robes of honour was the responsibility of the Keeper of the Privy Purse (nāẓir al-khāṣṣ), who supervised the Great Treasury (al-khizāna al-kubra), where the garments were stored. Al-Maqrizi provides a detailed description of the garments worn by the various classes and ranks; in addition, Mamluk practice included the bestowal of arms or even a fully outfitted horse from the Sultan's own stables as a tashrīf. The practice remained very common until the early 20th century; in 19th-century India, the bestowal gift or khillaut (khelat, khilut, or killut) might comprise from five up to 101 articles of clothing.
As the practice spread in the Muslim world, and robes began to be given for every conceivable occasion, they also acquired distinct names. Thus for example the khilaʿ al-wizāra ('robe of the vizierate') would be given on the appointment to the vizierate, while the khilaʿ al-ʿazl ('robe of dismissal') upon an—honourable—dismissal, the khilaʿ al-kudūm might be given to an arriving guest, while the khilaʿ al-safar would to a departing guest, etc.
Sums of money or other valuables were also given as part of the bestowal ceremony, or, in some cases, in lieu of the robe. In the Ottoman Empire, such a sum was known as khilʿet behā ('price of khilʿa'); most commonly this referred to the donativum received by the Janissaries on the accession of a new sultan.
