Walī (Arabic: ولي, plural ʾawliyāʾ أولياء) is an Arabic word whose literal meanings include "custodian", "protector", "helper", and "friend". In the vernacular, it is most commonly used by Muslims to indicate an Islamic saint, otherwise referred to by the more literal "friend of God". In the traditional Islamic understanding of saints, the saint is portrayed as someone "marked by [special] divine favor ... [and] holiness", and who is specifically "chosen by God and endowed with exceptional gifts, such as the ability to work miracles". The doctrine of saints was articulated by Islamic scholars very early on in Muslim history, and particular verses of the Quran and certain hadith were interpreted by early Muslim thinkers as "documentary evidence" of the existence of saints. Graves of saints around the Muslim world became centers of pilgrimage — especially after 1200 CE — for masses of Muslims seeking their barakah (blessing).
Since the first Muslim hagiographies were written during the period when the Islamic mystical trend of Sufism began its rapid expansion, many of the figures who later came to be regarded as the major saints in orthodox Sunni Islam were the early Sufi mystics, like Hasan of Basra (d. 728), Farqad Sabakhi (d. 729), Dawud Tai (d. 777–781), Rabia of Basra (d. 801), Maruf Karkhi (d. 815), and Junayd of Baghdad (d. 910). From the twelfth to the fourteenth century, "the general veneration of saints, among both people and sovereigns, reached its definitive form with the organization of Sufism ... into orders or brotherhoods". In the common expressions of Islamic piety of this period, the saint was understood to be "a contemplative whose state of spiritual perfection ... [found] permanent expression in the teaching bequeathed to his disciples". In many prominent Sunni Islamic creeds of the time, such as the famous Creed of Tahawi (c. 900) and the Creed of Nasafi (c. 1000), a belief in the existence and miracles of saints was presented as "a requirement" for being an orthodox Muslim believer.
Aside from the Sufis, the preeminent saints in traditional Islamic piety are the Companions of the Prophet, their Successors, and the Successors of the Successors. Additionally, the prophets and messengers in Islam are also believed to be saints by definition, although they are rarely referred to as such, in order to prevent confusion between them and ordinary saints; as the prophets are exalted by Muslims as the greatest of all humanity, it is a general tenet of Sunni belief that a single prophet is greater than all the regular saints put together. In short, it is believed that "every prophet is a saint, but not every saint is a prophet".
In the modern world, the traditional Sunni and Shia idea of saints has been challenged by movements such as the Salafi movement, Wahhabism, and Islamic Modernism, all three of which have, to a greater or lesser degree, "formed a front against the veneration and theory of saints." As has been noted by scholars, the development of these movements has indirectly led to a trend amongst some mainstream Muslims to resist "acknowledging the existence of Muslim saints altogether or ... [to view] their presence and veneration as unacceptable deviations". However, despite the presence of these opposing streams of thought, the classical doctrine of saint-veneration continues to thrive in many parts of the Islamic world today, playing a vital role in daily expressions of piety among vast segments of Muslim populations in Muslim countries like Pakistan, Egypt, Turkey, Senegal, Iraq, Iran, Algeria, Tunisia, Indonesia, Malaysia, and Morocco, as well as in countries with substantive Islamic populations like India, China, Russia, and the Balkans.
Regarding the rendering of the Arabic walī by the English "saint", prominent scholars such as Gibril Haddad have regarded this as an appropriate translation, with Haddad describing the aversion of some Muslims towards the use of "saint" for walī as "a specious objection ... for [this is] – like 'Religion' (din), 'Believer' (mu'min), 'prayer' (salat), etc. – [a] generic term for holiness and holy persons while there is no confusion, for Muslims, over their specific referents in Islam, namely: the reality of iman with Godwariness and those who possess those qualities." In Persian, which became the second most influential and widely-spoken language in the Islamic world after Arabic, the general title for a saint or a spiritual master became pīr (Persian: پیر, literally "old [person]", "elder"). Although the ramifications of this phrase include the connotations of a general "saint," it is often used to specifically signify a spiritual guide of some type.
Amongst Indian Muslims, the title pīr baba (पीर बाबा) is commonly used in Hindi to refer to Sufi masters or similarly honored saints. Additionally, saints are also sometimes referred to in the Persian or Urdu vernacular with "Hazrat." In Islamic mysticism, a pīr's role is to guide and instruct his disciples on the mystical path. Hence, the key difference between the use of walī and pīr is that the former does not imply a saint who is also a spiritual master with disciples, whilst the latter directly does so through its connotations of "elder." Additionally, other Arabic and Persian words that also often have the same connotations as pīr, and hence are also sometimes translated into English as "saint", include murshid (Arabic: مرشد, meaning "guide" or "teacher"), sheikh and sarkar (Persian word meaning "master").
In the Turkish Islamic lands, saints have been referred to by many terms, including the Arabic walī, the Persian s̲h̲āh and pīr, and Turkish alternatives like baba in Anatolia, ata in Central Asia (both meaning "father"), as well as eren or ermis̲h̲ (< ermek "to reach, attain") or yati̊r ("one who settles down") in Anatolia. Their tombs, meanwhile, are "denoted by terms of Arabic or Persian origin alluding to the idea of pilgrimage (mazār, ziyāratgāh), tomb (ḳabr, maḳbar) or domed mausoleum (gunbad, ḳubba). But such tombs are also denoted by terms usually used for dervish convents, or a particular part of it (tekke in the Balkans, langar, 'refectory,' and ribāṭ in Central Asia), or by a quality of the saint (pīr, 'venerable, respectable,' in Azerbaijan)."