Those conditions when ghusl is wajib (obligatory)

1. A disbeliever accepts Islam and while he was in the state of kufr he experienced hadath-e-akbar. He did not have a bath, or if he did, it was not considered to be a valid ghusl in Islam. After accepting Islam, ghusl will become wajib on him.

2. If a person reaches puberty before the age of fifteen and he experiences his first wet dream. As a precaution, ghusl will be wajib on him. If he has any wet dreams after this or after the age of fifteen, ghusl will be fard.

3. To give a bath to the dead body of a Muslim is fard-e-kifayah.