Mawla: Friend or Guardian?
Studying the old lexical, literal, and commentary texts shows that Mawla means “guardian”, “being more appropriate than the believers”, and “having more authority upon the believers than themselves”. Some statements in which Mawla is used with these meanings are as follows:
Abu Ubaydah Ma’mar ibn Mathna has explained the meaning of the word Mawlakum in verse 15 of Sura Hadid: “…Your abode is the fire, it is your friend, and evil is the resort” and said that: “It is appropriate for you.”  His commentary is based on the poem of Labid, the writer of one of the Mo’llaqat Sab’, the seven great Arabic poems written in the pre-Islamic Age of Ignorance: “The wild cow is so frightened, thinking the owner of hunting dogs is both in front of you and behind it.” The commentators of Mo’llaqat Sab’ have interpreted Mawla as meaning the owner. 
Famous Kufic writer and commentator, Abu Zakariyya Yahya ibn Ziyad ibn Abdullah, known as Farra, has commented on the same verse and said that: “‘He is your Mawla’ means that he is more appropriate than you.”  Abul-Hasan Akhfash, Abu Ishaq Zajjaj, and Muhammad ibn Qasim Anbazi also have the same view.  Muhammad ibn Sa’ib Kalbi – the great author, commentator, and ethnologist – has commented on the verse 51 of Sura Tawba: “Say, Nothing will afflict us save what Allah has ordained for us; He is our Patron, and on Allah let the believers rely.” He said that “Allah has more authority over our life and death than ourselves.” 
As mentioned above, “guardian” and “administrator of the affairs” are the obvious meanings of Mawla confirmed by many, such as:
Abul Abbas Muhammad ibn Yazid, known as Mubarrad, has commented on verse 11 of Sura Muhammad: “That is because Allah is the Protector of those who believe…” In this way, “‘Wali’ and ‘Mawla’ have the same meaning as this: one who is more appropriate than all the people and is the guardian of their affairs.”  Farra has also written that “Wali and Mawla have the same meaning in the Arabic language.” 
Raghib Isfahani, the great commentator, and writer and researcher of Qur’an during the fourth century, has also written that “Wilayah means guardianship, and both Wali and Mawla are used in this meaning, and in the subjective meaning (Muwali) and in the objective meaning (Muwali).” 
Abul Hasan Ali ibn Ahmad Wahedi Neyshaburi, the great commentator and writer of the 5th century, has said about Sura Anam’s verse 62: “Then they are sent back to Allah, their Master, the True one” has said that: “Mawla means one who takes charge of their affairs.” 
There are many learned men confirming this reality, but we make suffice to mention someone else. Jarollah Zimakhshari, the great Mu’tazilite writer and commentator, has commented on verse 286 of Sura Baqara: “You are our Patron, so help us against the unbelieving people”. In this way, “You are our master, and we are Your servants; You are our assistance; You are our guardian.” 
Ibn Athir, in his famous work al-Nihayah in which he has explained the meaning of difficult words, has written: “Mawla has been used in the traditions repeatedly, and it is a noun which has several meanings…and whoever takes charge of an affair or rises for establishing it, will be its Mawla and Wali…one of the traditions is this: ‘The marriage of a woman marrying without the permission of her Mawla will be void.’ In another narration of this tradition, (instead of her Mawla) her Wali (guardian of her affair) has been used.” 
Therefore, it is clear that “being more appropriate”, “guardianship of the affairs”, “leadership” and “headship” are meanings which can be found for the word “Mawla”, and that Mawla and Wali have the same meaning. These are obvious realities confirmed by great writers, learned men, and commentators. As a result of this, we believe that – as do the followers of the other schools – the Prophet (peace be upon him and his progeny), through his defining statement in that wonderful and eternal event of Ghadir-e-Khumm, determined the Wilayat and Imamate and Guardianship of Ali (peace be upon him).
The only reason for holding that great meeting was for people to become aware of the Wilayat of Ali in a clearer and more useful way and to not raise excuses in the future, such as “We didn’t hear it”, “We were not aware of this”, and so on. Therefore, the Prophet called people to testify about that many times, and at the end of the meeting, he said loudly: “Beware! The present must deliver this message to the absent.” 
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2. Sharh al-Mu`allaqat al-Sab`, Abu `Abdullah Husayn ibn Ahmad Zuzani, p.210. Sharh al-Qasaid al-Sab` al-Tawal al-Jahiliyyat, Abu Bakr Muhammad ibn Qasim al-Anbazi, pp.565-566.
3. Ma`ani al-Qur’an, vol.3, p.124. Tafsir al-Fakhr al-Razi, vol.29, p.228.
4. Nafahat al-Azhar, vol.8, pp.16-86. Al-Ghadir, vol.1, p.615.
5. Al-Bahr al-Mohit, vol.5, p.53.
6. Al-Shafi, vol.2, p.271.
7. Ma`ani al-Qur’an, vol.2, p.161. Al-Shafi, vol.2, p.271.
8. Mufradat Alfaz al-Qur’an, the matter: Wali.
9. Al-Wasit fi Tafsir al-Qur’an al-Majid, vol.2, p.281.
10. Al-Kashshaf, vol.1, p.173.
11. Al-Nihayah fi Gharib al-Hadith, the matter: Wali.
12. Encyclopedia of Amir al-Muminin (a.s.), vol.1, p.540.