What is the ruling on one who omits the invocation of Allah's name during his ablution and does not remember it until after he has finished the ablution?

The questioner : What is the ruling on one who omits the invocation of Allah's name during his ablution and does not remember it until after he has finished the ablution?

The Shaykh : Praise be to Allah, Lord of the worlds, and may blessings and peace be upon our Prophet Muhammad, the Seal of the Prophets and the Imam of the righteous, and upon his family and his Companions, and those who follow them with excellence until the Day of Judgment.
If one forgets to invoke the name of Allah during his ablution until he has finished it, he owes nothing and his ablution is valid. Even if it is assumed that he intentionally omitted the invocation during his ablution, there is a difference of opinion among scholars regarding the validity of his ablution. Some say that his ablution is valid and he owes nothing, because the numerous hadiths from the Prophet (peace and blessings be upon him) describing his ablution do not mention the invocation. The hadith: is not authentically traced to the Prophet (peace and blessings be upon him), as al-Hafiz Ibn Hajar mentioned in *Bulugh al-Maram* that Imam Ahmad (may Allah have mercy on him) said: "Nothing is established in this chapter".
Some scholars held that invoking the name of Allah during ablution is obligatory, and that if one intentionally omits it, his ablution is not valid. However, the first opinion is closer to the truth, meaning that invoking the name of Allah during ablution is a recommended practice (sunnah). If a person does it, it is more complete and better; if he does not do it, his ablution is valid.

The questioner : May Allah bless you.