The Ruling on the Mention of Allah's Name During Ablution

Question:
The questioner, 'Ayd, says: Honorable Shaykh, regarding the mention of Allah's name during wudu' (ablution), is it obligatory? And if a person leaves it out, does he owe anything?

Answer:
The mention of Allah's name in wudu' is prescribed by consensus, but the majority hold that it is recommended, while Imam Ahmad holds that it is obligatory. The saying of the Messenger (peace and blessings be upon him) has come through multiple chains that strengthen one another.
Imam Ahmad interpreted it to mean that the negation refers to the reality of the act, not that the wudu' is invalid, whereas the majority interpreted it to mean the negation of perfection, meaning that the wudu' of one who does not mention Allah's name is not complete. In any case, it is prescribed by consensus, but whether it is obligatory or recommended is where the disagreement lies. It is said at the beginning of the wudu': "There is no god but Allah."