Obligatory and recommended ghusls

It is narrated from Sayyiduna Abdullah bin Amr (may Allah be pleased with them both) that he said: "Ghusl is (Sunnah or required) for five reasons: after cupping (hijamah), after going to the hammam (public bathhouse), from janabah (major impurity), after washing the dead, and for Friday." The narrator says: When this was mentioned to Imam Ibrahim al-Nakha'i, he said: "They (the Companions and the predecessors) did not consider any ghusl obligatory except the ghusl of janabah, but they considered bathing on Friday recommended and commendable."
Imam Abu Bakr bin Abi Shaybah recorded this narration in his work "al-Musannaf"; it clarifies the various causes of purification and the legal status and ranks of ghusl according to the leading jurists of that era.

It is narrated from Sayyidah Aishah (may Allah be pleased with her) that she said: "When one of you is in the state of janabah (major impurity), he must not sleep (without performing ablution), for he does not know; perhaps his soul may be taken during his sleep."
The chain of this report is sahih (authentic), and Imam Ibn Abi Shaybah narrated it in 'al-Musannaf' (hadith: 197).