AsalamoAlikum
My Question is with regard to ghusl
During ghusl do we have to just rinse the mouth or do we have to gargle as well(taking water down to the throat)? is it true that without gargling ghusl is not complete? if gargling is essential than can we do it while rinsing the mouth during beginning wudu(the sunnat way) since normally we do not gargle in wudu and i am afraid whether doing so would be counted as bidat. In the sequence of sunnat way of ghusl usually posted on websites I do not find gargling so basically I am confused whether I have to do it or not and when to position it.
Do we have to make sure that water reaches inside the ears for ghusl to be accptable and if yes than to what extent?
Jazak Allah

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

Rinsing the mouth is something legislated, be it obligatory or desirable, according to two different views of the jurists . As regards gargling (making water reach the throat), and the like, then no scholar has ever said that it is legislated, and this act may be considered as exaggerating in religion. What is required in Ghusl (ritual bath) is to make water reach all the external parts of the body, and not reach inside the body. Hence, it is obligatory (in the ritual bath) to make the water reach all the external parts of one’s body, including the inside and outside of the ears.

Concerning the ear canal, then the scholars differed in opinion about the obligation of washing it.  The Maaliki School of jurisprudence is of the view that it is a Sunnah to rub it when performing Ghusl. However, the Hanafi School of jurisprudence is of the view that it is an obligation to wash everything that could be washed without difficulty, like the ear (ear canal) and the belly button. Whereas the Shaafi’i School of jurisprudence is of the opinion that it is an obligation to wash what appears from the ear canal and not the inside of it, as stated by An-Nawawi .

For more benefit on how to perform Ghusl according to the Sunnah, please refer to Fatwa 82245.

Allaah Knows best.