Is Wiping Neck in Wudu Obligatory?
Question

Is it recommended to wipe the neck during Wudu?
Praise be to Allah.It is not recommended to wipe the neck during Wudu because there is no proof of that from the Prophet (peace and blessings of Allah be upon him). 
Shaykh Al-Islam Ibn Taymiyah (may Allah have mercy on him) said: 
“There is no authentic report from the Prophet (peace and blessings of Allah be upon him) which says that he wiped his neck during Wudu , rather no such thing has been narrated from him in any authentic Hadith. Rather the authentic Hadiths which describe the Wudu of the Prophet (peace and blessings of Allah be upon him) do not mention that he wiped his neck. Hence the majority of scholars, such as Malik, Ash-Shafi`i and Ahmad did not regard that as recommended. Those who say that it is recommended rely on a report narrated from Abu Hurayrah (may Allah be pleased with him) or an inauthentic Hadith which says that he wiped his head until he reached the back of his head. Such reports cannot be relied on, and it does not contradict what is indicated by the sound Hadiths. Whoever does not wipe his neck, his Wudu is valid according to scholarly consensus.” (Majmu` Al-Fatawa, 21/127) 
This Hadith, “He (peace and blessings of Allah be upon him) wiped his head until he reached the back of his head (which is the beginning of the back of the head),” was narrated by Abu Dawud (132) and was classed as inauthentic  by Al-Albani in Da`if Abu Dawud. 
In Al-Majmu` (1/489) An-Nawawi (may Allah have mercy on him) mentioned a difference of opinion among the companions of Ash-Shafi`i (may Allah have mercy on him) concerning wiping the neck in Wudu. Then he said: This is a summary of what they said, and they had four views on this matter, one of which is that it is Sunnah to wipe it with new water. The second is that it is recommended and cannot be said to be Sunnah. The third is that it is recommended to use the water left from wiping the head and ears . The fourth is that it is neither Sunnah nor recommended. The fourth view is the one that is correct. Hence Ash-Shafi`i (may Allah have mercy on him) did not mention it, and neither did our earlier companions. It was not mentioned by most of the scholars. There is no proof of that from the Prophet (peace and blessings of Allah be upon him). 
It is proven in Sahih Muslim and elsewhere that the Prophet (peace and blessings of Allah be upon him) said: “The worst of matters are those which are newly-invented, and every innovation is a going astray.” 
It is narrated by Al-Bukhari and Muslim that the Prophet (peace and blessings of Allah be upon him) said: “Whoever introduces anything into our religion that is not part of it, will have it rejected.” According to a version narrated by Muslim: “Whoever does any action that is not in accordance with this matter of ours will have it rejected.” 
With regard to the Hadith that is narrated from Talhah ibn Musarraf, from his father, from his grandfather, which says that he saw the Messenger of Allah (peace and blessings of Allah be upon him) wiping his head until he reached the back of his head and the first part of the neck, it is a Hadith which is inauthentic according to scholarly consensus. 
With regard to the words of Al-Ghazali (may Allah have mercy on him): Wiping the neck is Sunnah because the Prophet (peace and blessings of Allah be upon him) said, “Wiping the neck is a protection from the yoke (or chains – Al-Ghull)”, this is a mistake, because these are not the words of the Prophet (peace and blessings of Allah be upon him).”
Al-Ghull (pl. Al-Aghlal) refers to chains that are placed on the neck. Allah says (interpretation of the meaning): 
“They are those who disbelieved in their Lord! They are those who will have iron chains (Al-Aghlal) tying their hands to their necks.” [Al-Ra`d 13:5] 
“And We shall put iron collars (Al-Aghlal) round the necks of those who disbelieved. Are they requited aught except what they used to do?” [Saba’ 34:33]
Ibn Al-Qayyim (may Allah have mercy on him) said in Zad Al-Ma`ad (1/195): 
“There is no authentic Hadith from the Prophet (peace and blessings of Allah be upon him) about wiping the neck at all.”
 Shaykh Ibn Baz (may Allah have mercy on him) said: 
“It is not recommended or prescribed in shari`ah to wipe the neck, rather the head and the ears only are to be wiped, as is indicated by the Quran and Sunnah.” (Majmu` Fatawa Ibn Baz, 10/103)
And Allah knows best.