Protector, Guardian, Supporter, Helper, Friend etc. [plural ‘Auliyâ] see 33:17
The wali is the represention/mediator/guardian for women seeking marriage.
Who Needs a Wali for Marriage?
Men do not need a wali.
Women who have previously had marital relations with a man, can represent themselves and do not have to have a wali for seeking the husband, but they WILL need a wali for the actual marriage contract, i.e. Regardless, she still must not be alone with a non-mahram man, and she MAY of course, and is encouraged to, have a wali be involved to whatever level she is comfortable with. All of this is for her protection, so that she may be protected from inquiries by inappropriate men and possibly “fall in love” and regret it later. This way, the men’s character is first screened for her, still leaving her with the ultimate decision.
Note that it may be argued that new reverts to Islam are as innocent as a virgin (since all sins are forgiven upon embracing Islam) and is recommended for new muslimahs have a wali for seeking marriage.
The Prophet (sallallahu aleihi wa sallam) said: “A guardian has no concern with a woman previously married and has no husband, and an orphan girl (i.e. virgin) must be consulted, her silence being her acceptance.” [Sunan of Abu Dawud 2095, Narrated Abdullah ibn Abbas]
Malik bin Anas told us from ‘Abdallah bin yazid- freed slave of al-aswad bin sufyan- from Abu Salma bin AbdalRahman from Fatimah, daughter of Qays who said,: Her husband divorced her and the Apostle of Allah ordered her to fullfil the ‘Iddah in the house of Ibn Umm Maktum before she could lawfully remarry, and told her to let him know when she had become lawful for remarriage. When the time had come, she told him that Mu’awiyah bin Abu Sufyan and Abu Jahm had proposed to her…
Umm Salamah, r.a., a widowed woman, was proposed in marriage by Abu Bakr, and refused. Then she was proposed to by Umar and she refused. Then she was proposed to by Prophet Muhammad saaws and accepted. [source: The Alim for Windows release 4.51, Biography of Umm Salamah]
In all cases, the woman must consent to the marriage or the marriage can be ruled invalid. Virgins need not speak up to declare that they want a marriage; simply not speaking out against the marriage (her silence) is sufficient consent for a virgin.
Malik related to me from Abdullah ibn al-Fadl from Nafi ibn Jubayr ibn Mutim from Abdullah ibn Abbas that the Messenger of Allah, SAAWS, said, “A woman who has been previously married is more entitled to her person than her guardian, and a virgin must be asked for her consent for herself, and her consent is her silence ” [Malik’s Muwatta, Book 28, Number 28.2.4]
The Prophet saaws said, “A matron should not be given in marriage except after consulting her; and a virgin should not be given in marriage except after her permission.” The people asked, “O Allah’s Apostle! How can we know her permission?” He said, “Her silence (indicates her permission).” [Sahih Al-Bukhari 7.67]
Narrated Khansa bint Khidam Al Ansariya “…that her father gave her in marriage when she was a matron and she disliked that marriage. So she went to Allah’s Apostle and he declared that marriage invalid.” [Sahih Al-Bukhari 7.69]
“…Her guardian should not make a promise (to somebody to get her married to him) without her knowledge…” [Sahih Al-Bukhari 7.56]
Women who are virgins must have a wali when getting married.
“No marriage is valid without a wali.” [related by Ahmed and others and deemed sound by Ahmed, Ibn Hajar and others]
The Prophet SAAWS said: “There is no marriage without the permission of a guardian.” [Sunan of Abu Dawood 2080, Narrated Abu Musa]
“When a woman marries without the permission of her wali, then her marriage is not valid, not valid, not valid.” [Related by Ahmad, Tirmidhi and others. Tirmidhi said, this is a hasan Hadith]
If the woman does not have a male mahram relative, the Imam closest to her locality, of the same faith as her, becomes her wali.
“If they dispute, then the sultan (man in authority) is the wali of those who have no wali.” [Dawud 2078, Narrated ‘Aisha , also related by Tirmidhi and others. Tirmidhi said, this is a hasan Hadith. Ibn Majah and Imam Ahmad, Hadith number 1880; also in Salih al-Jaami’, hadeeth number 7556.) Shaykh Al Albaanee declares it authentic in Saheeh Al Jaami’ vol. 2, no. 7556. ]
“The believers, men and women, are awilyaa’a (allies and protectors) of one another.” [The Noble Qur’an 9:71]
“…And never will Allâh grant to the disbelievers a way (to triumph) over the believers. [The Noble Qur’an 4:141]
“O you who believe! Take not for Auliyâ’ (protectors or helpers or friends) disbelievers instead of believers. Do you wish to offer Allâh a manifest proof against yourselves?” [The Noble Qur’an 4:144]
“And those who disbelieve are allies to one another…” [The Noble Qur’an 8:73]
If the wali is non-mahram, such as is the case with many new reverts to Islam, she should avoid ever being alone with him.
“A man is never alone with a woman except that shaitan will be the third.” (Related by Ahmed and Tirmidhi)