Source: Ahkam wa Masail in the Light of the Qur'an and Hadith, Volume 02
The Hadith, "His Wudu is not valid who does not mention the name of Allah over it," is classified as Hasan (good) due to supporting narrations.
(Sunan Abu Dawood, Chapter: Saying Bismillah for Wudu, Hadith: 101)
Scholars of Hadith such as Hafiz Mundhiri رحمه الله have graded this narration as Hasan based on corroborating evidences.
If someone forgets to say Bismillah at the beginning of Wudu and remembers during Wudu, it is recommended (Mustahabb) to say it immediately upon remembering.
If they do not remember until after completing Wudu, the Wudu is still considered valid, and there is no need to repeat it, because forgetfulness is excused in Shari‘ah.
➊ The Hadith on saying Bismillah before Wudu is Hasan, and while it emphasizes its importance, forgetting to say it does not invalidate the Wudu.
➋ If one remembers during Wudu, saying Bismillah at that point is Mustahabb, and no repetition of Wudu is required in case of forgetfulness.
✿ Ruling on Omitting Bismillah Before Performing Wudu
The Hadith, "His Wudu is not valid who does not mention the name of Allah over it," is classified as Hasan (good) due to supporting narrations.
(Sunan Abu Dawood, Chapter: Saying Bismillah for Wudu, Hadith: 101)
Scholars of Hadith such as Hafiz Mundhiri رحمه الله have graded this narration as Hasan based on corroborating evidences.
➊ What if One Forgets to Say Bismillah?
If someone forgets to say Bismillah at the beginning of Wudu and remembers during Wudu, it is recommended (Mustahabb) to say it immediately upon remembering.
If they do not remember until after completing Wudu, the Wudu is still considered valid, and there is no need to repeat it, because forgetfulness is excused in Shari‘ah.
❖ Summary
➊ The Hadith on saying Bismillah before Wudu is Hasan, and while it emphasizes its importance, forgetting to say it does not invalidate the Wudu.
➋ If one remembers during Wudu, saying Bismillah at that point is Mustahabb, and no repetition of Wudu is required in case of forgetfulness.
