Ruling on rubbing the body with a sponge or loofah when doing ghusl?

In
the answer to question no. 93056, we stated that
when doing ghusl in the case of janaabah, it is sufficient to ensure that
water reaches all of the body, and that rubbing or passing the hands over
the body when doing ghusl is not obligatory according to the majority of
scholars (may Allah have mercy on them), apart from Maalik and some of the
scholars who agreed with him (may Allah have mercy on them). 

An-Nawawi
(may Allah have mercy on him) said: Our view is that rubbing the parts of
the body when doing ghusl and wudoo’ is Sunnah, not obligatory. If he pours
water over himself and makes it reach every part without touching it with
his hand, or he immerses himself in a large amount of water, or he stands
beneath a downspout or in the rain with the intention of doing ghusl, and it
reaches his hair and his skin, this is acceptable for wudoo’ and ghusl. This
is the view of all the scholars, except Maalik and al-Muzani, who stipulated
that rubbing the skin is essential for ghusl and wudoo’ to be valid.

End
quote from al-Majmoo‘, 2/215 

Based
on that, if a person does ghusl by pouring water over the body and making
the water reach every part of the body, this is what is required. If he does
more than that, by rubbing his body with a sponge or loofah whilst doing
ghusl, there is nothing wrong with that, but it is not obligatory and is not
a condition of ghusl being valid, as stated above. 

This
ruling only applies in the case of someone who combines pouring water over
the body with rubbing it with a sponge and the like whilst doing ghusl. 

But
if what is meant in the question is the ruling on only passing the sponge
over the body whilst doing ghusl, without pouring water on oneself, and
being content with whatever dampness gets onto the body from the sponge,
then in this case his ghusl is not valid, unless he squeezes the sponge and
water flows from it onto his body. In that case, ghusl as prescribed in
Islam is done by means of this water that flows onto the body, not by means
of merely passing the sponge over the body, even if it is wet. 

For
more information on washing the head and the hair in the case of janaabah,
please see the answer to questions no. 27065 and
163816 

And
Allah knows best.