(a) It is narrated from Sayyidah Aishah (may Allah be pleased with her) that Sahlah bint Suhayl began to have istihadah (irregular bleeding). She came to the Prophet (peace and blessings be upon him), and he (peace and blessings be upon him) ordered her: "She should perform a ritual bath (ghusl) for every prayer." When that became exhausting for her, he (peace and blessings be upon him) ordered her: "She should pray Zuhr and Asr with one ghusl, and Maghrib and Isha with one ghusl, and perform a separate ghusl for the morning prayer."
(b) It is narrated from Sayyidah Aishah (may Allah be pleased with her) that the Messenger of Allah (peace and blessings be upon him) had ordered Sahlah bint Suhayl (may Allah be pleased with her) to perform ghusl for every prayer; when this became difficult for her, he (peace and blessings be upon him) ordered her (and he mentioned the rest of the hadith).
(c) Abu Bakr bin Ishaq says that some of our shaykhs said: No one except Muhammad bin Ishaq narrates this hadith (with a connected chain); Imam Shu'bah did not narrate this hadith from the Prophet (peace and blessings be upon him) and denied that it is marfu' (attributed to the Prophet), and he also declared the name of the woman with istihadah to be mistaken.
(d) Imam Abu Bakr says: The narrators differ over the chain of this hadith.
(e) The Shaykh (may Allah have mercy on him) says: Shu'bah and Muhammad bin Ishaq narrated it as has already passed.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحيض / 1655