Is the wudu' of one who forgets the bismillah valid or not?

Question:
Is the wudu' of one who forgets the bismillah valid or not? The prescription of the command to say the bismillah in wudu' is established in the saying of the Messenger of Allah (peace and blessings be upon him): "There is no wudu' for the one who..." This hadith has been transmitted through numerous chains that reinforce one another, until some of the scholars of hadith said, "We are certain that the Messenger of Allah (peace and blessings be upon him) said it," due to the multiplicity of its routes.

Answer:
So, is the bismillah prescribed at the beginning of wudu', in that one says "Bismillah"? However, the scholars differed on whether its prescription is from the category of obligation or from the category of recommendation?
The majority hold that its prescription is from the category of recommendation, and that the saying is for the sake of perfection. Imam Ahmad (may Allah have mercy on him) held that this prescription is from the category of obligation, so the wudu' of a Muslim is not valid unless he says "Bismillah" at the beginning of his wudu'. If he leaves it out due to forgetfulness, his wudu' is valid. So, it is obligatory for him with remembrance, and it is dropped with forgetfulness. He interpreted the saying as a negation of the reality (of the wudu'). This is a position that has its merit. It is emphasized for the Muslim to remember the name of Allah at the beginning of wudu'. If he leaves it out due to forgetfulness, leaving it out in forgetfulness, then his wudu' is valid, based on the saying of the Messenger of Allah (peace and blessings be upon him) and the saying of Allah the Exalted May Allah reward you with good, and may He do you good.