Is it obligatory to remove impurity and perform istijmar from feces before ghusl, or is it permissible to delay istijmar until after it? And does speaking or singing during ghusl or istinja' affect their validity? And does eating garlic and onions before ghusl affect its validity, and is it obligatory to clean the teeth before it?

The impurity itself must be removed before performing the purificatory bath (ghusl) from Janabah (ritual impurity requiring ghusl) by using water (istinja') or stones/toilet paper (istijmar); this is because its persistence will contaminate the water and invalidate the ghusl. A group of jurists holds the view that istinja' is a condition for the validity of both wudu' (ablution) and ghusl. As for talking or singing during ghusl, it does not affect its validity; it is permissible during ghusl, but disliked when answering the call of nature. The persistence of the smell of garlic and onions does not affect the validity of wudu' or ghusl.