Question Summary:
Is Ghusl valid if water did not reach the gums?

Question Detail:

Asalamu Alaykum, Moulana, I want to ask that is my ghusl invalid if I think that when I rinsed my mouth, the water didn't reach the gums. Then I prayed salaah, so is my salaah valid? I performed ghusl as I saw a brown particle in my underwear . There wasn't any wetness.

Answer :

In the Name of Allah, the Most Gracious, the Most Merciful.
As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.
There are two aspects to your query;
1) According to the most correct opinion in the Hanafi Madhab, gargling is not necessary for the validity of ghusl. Rinsing the mouth is sufficient, albeit contrary to the Sunnah.[1]
2) Ghusl is not obligatory if a brown particle is seen on the underwear.[2]
And Allah Ta’āla Knows Best
Saad Haque
Student Darul Iftaa
New Jersey, USA 
Checked and Approved by,
Mufti Ebrahim Desai.