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Wipe water over head/hair 1 times
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It has been recorded that the Prophet(peace and blessings of Allaah be upon him) used to wipe his head three different ways:
1.
Wiping all of his head
'Abdullah ibn Zaid reported that the Prophet(peace and blessings of Allaah be upon him) wiped his entire head with his hands. He started with the front of his head, then moved to the back, and then returned his hands to the front.
2.
Wiping over the turban only
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Said 'Amru ibn Umayyah, "I saw the Messenger of Allah(peace and blessings of Allaah be upon him) wipe over his turban and shoes." (Related by Ahmad, al-Bukhari and Ibn Majah).
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Bilal reported that the Prophet(peace and blessings of Allaah be upon him) said, "Wipe over your shoes and head covering." (Related by Ahmad.)
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'Umar once said, "May Allah not purify the one who does not consider wiping over the turban to be purifying." Many hadith have been related on this topic by al-Bukhari, Muslim and others. Most of the scholars agree with them.
3.
Wiping over the front portion of the scalp and the turban
Al-Mughirah ibn Shu'bah said that the Messenger of Allah, upon whom be peace, made ablution and wiped over the front portion of his scalp, his turban and his socks. (Related by Muslim.) There is, however, no strong hadith that he wiped over part of his head, even though al-Ma'idah: apparently implies it. It is also not sufficient just to wipe over locks of hair that proceed from the head or along the sides of the head.
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If you are a female and a non-mahram male (or any non-Muslim who you believe may describe you to others) may see you (such as in a public bathroom, etc.), do not remove your hijab or niqab... keep it on and wipe over it.
http://muttaqun.com/wudu.html
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"
O you who believe, when you observe the Contact Prayers (Salat) you shall wash your faces, wash your arms to the elbows, wipe your heads and wash your feet to the ankles." 5:6
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Wiping the Head
Wipe the head with the fingers of both hands, starting from the forehead, taking them to the nape of the neck, then bring them back to the forehead. Do this one time.
Allah (SWT) said, "O you who believe! When you intend to offer prayer, wash your faces and your hands (fore-arms) up to the elbows, rub (by passing wet hands over) your heads, and (wash) your feet up to ankles…" (Al-Ma'idah 5:6)
The Prophet (SAW) wiped his head with his two hands, moving them forwards and backwards - beginning with the front of the head and (wiping) with them up to his nape then he (SAW) returned them to the place from which he began. (Sahih Al-Bukhari, Muslim, At-Tirmithee, and others)
Wiping Over the Turban
Men who wear a head piece that is difficult to remove (such as a turban) should wipe over the head covering. Do this one time.
Amr ibn Umayyah (RA) said, "I saw Rasoolullah (SAW) wipe over his turban and leather socks." (Sahih - Al-Bukhari and others)
Wiping Over the Turban and Forelock
If part of the head is uncovered and it is normally so, then it is preferable to wipe over the part that is uncovered along with the turban. Do this one time.
Shu'bah (RA) said, "The Messenger of Allah (SAW) made wudu and wiped over the front portion of his scalp, his turban and his socks. (Sahih - Muslim)
Woman's Head Cover
As for the woman's head cover, it is also permissible to wipe over it. This would be the case of a woman that has no private place for wudu (i.e. where non-Mahram men or non-Muslim women may see them). Do this one time.
Umm Salamah (RA) used to wipe over her head cover . (See'al-Mughnee' - Ibn Mundhir)
http://www.themuslimwoman.com/chooseyourpath/basicguidetoprayer/wudu.htm