Mentioning Allah's Name for Wudhu' in the Toilet is done in the Heart
Question :
When I want to perform Wudhu', I make the intention to perform Wudhu' for prayer, but I do not mention Allah's Name when I am in the toilet, although I know the Hadith which says:
"There is no Wudhu' for the one who did not mention Allah's Name upon it.
What is the ruling on this?
Answer:
Mentioning Allah's Name when one is in the toilet should be done in the heart and it should not be spoken aloud, so you should act upon this, since the most authoritative view holds that mentioning Allah's Name is not obligatory, but preferred, so you should not worry or think too much about it.
Source:
Ibn 'Uthaimin
Fatawa Islamiyah, Vol. 2 Page 74