Is Wiping the Ears Compulsory in Wudu?
Question

If you take Wudu, and say the Shahadah, and get ready for prayer, but then suddenly you remember that you forgot to wash your ears. What must I do? Retake Wudu from the beginning or just go and wash the ears?
Praise be to Allah.Wiping the ears in Wudu is something that the Prophet (blessings and peace of Allah be upon him) always did, and the scholars differed concerning it as to whether it is obligatory or Sunnah. Some of them said that it is obligatory, as is the view of the Hanbalis, because of the report narrated by Ibn Majah from `Abdullah ibn Zayd (may Allah be pleased with him) who said: The Messenger of Allah (blessings and peace of Allah be upon him) said: “The ears are part of the head.” There is some difference of opinion as to whether this Hadith is authentic; it was classed as authentic by Al-Albani in Sahih Ibn Majah. 
If the ears are part of the head, then wiping them in Wudu is obligatory, as is wiping the head . 
But the majority are of the view that wiping the ears is Sunnah and recommended, but is not obligatory. (See: Al-Mawsu`ah Al-Hadithiyyah, 43/364) 
What is narrated from Imam Ahmad (may Allah have mercy on him) is that if a person omits to wipe his ears, his Wudu is still valid. 
Ibn Qudamah (may Allah have mercy on him) said in Al-Mughni, 1/90: 
“The ears are part of the head , so by analogy our view is that it is obligatory to wipe them when wiping the head. Al-Khallal said: All of them narrated from Abu `Abdullah [i.e., Imam Ahmad] concerning the one who does not wipe them, either deliberately or out of forgetfulness, that it is still valid. That is because they belong to the head, but we do not understand that the word head refers to the ears too, and they do not resemble any part of the head. Hence wiping them does not count as wiping the head according to those who say that wiping part of the head is sufficient. But it is better to wipe them when wiping the head, because the Prophet (blessings and peace of Allah be upon him) wiped them when he wiped his head. Ar-Rubayyi` (may Allah be pleased with her) narrated that she saw the Prophet (blessings and peace of Allah be upon him) wipe his head, front and back, and his temples and ears once. Ibn `Abbas (may Allah be pleased with him) narrated that the Prophet (blessings and peace of Allah be upon him) wiped his head and his ears, inside and out. At-Tirmidhi said: The Hadith of Ibn `Abbas and the Hadith of Ar-Rubayyi‘ are both authentic.”
Based on that, if a person forgets to wipe his ears, he is fine and his Wudu is valid. 
And Allah knows best.