Answered by Shaykh Faraz Rabbani
Many people have said to me that wiping the neck is an innovation and is forbidden.
What is the ruling of wiping the neck in wudu?
Answer: Walaikum salam,
1. Wiping the nape [‘the back part of the neck’ – Webster’s] is recommended. [Nur al-Idah, Durral-Mukhtar, Hadiyya al-Ala’iyya]
2. Wiping the front of the neck is disliked and an innovation. [ibid.]
As for Imam Nawawi’s opinion that it is an innovation due to the evidence for it being excessively weak, this was not accepted by many other hadith experts.
Among the wisdom behind wiping the back of the neck is that it is from completely wiping the head, front and back.
And Allah alone gives success.