What is required when doing ghusl in the case of major impurity is to make the water reach every part of the body. It is not stipulated that soap or any other cleansing material be used, because none of those who described the ghusl of the Prophet (blessings and peace of Allah be upon him) in the case of janaabah said anything about him using lotus leaves or any other kind of cleansing material. Rather all he (blessings and peace of Allah be upon him) did was to pour water over his body and make it reach every part.
For example, Aa'ishah (may Allah be pleased with her) narrated that the Prophet (blessings and peace of Allah be upon him), when he did ghusl in the case of janaabah, used to pour three scoops of water with his hands, then pour water over all of his skin. Narrated by al-Bukhaari, 240
It was narrated that Umm Salamah (may Allah be pleased with her) said: I said: O Messenger of Allaah, I am a woman with tightly braided hair; should I undo it for ghusl from janaabah? He said: No; it is sufficient for you to pour three handfuls of water over your head, then pour water over you, and you will become pure. Narrated by Muslim, 330.
The scholars of the Standing Committee were asked (5/315): Should one wash with soap after janaabah, and why?
They replied: It is obligatory to do ghusl for janaabah using water, but it is not essential to use cleansing materials such as soap and the like. This is what is indicated by the Sunnah of the Prophet (blessings and peace of Allah be upon him). But if one uses soap or some other cleansing material, there is nothing wrong with that.
And Allah knows best.
Reproduced from Islam QA