Abu 'Abd al-Rahman said: This is an error.

33 - Chapter: Mention of the hadith of Abu Salama concerning that (1)

2175 - Shu'ayb ibn Yusuf and Muhammad ibn Bashshar informed us — and the wording is his — they said: 'Abd al-Rahman narrated to us, he said: Sufyan narrated to us, from Mansur, from Salim, from Abu Salama,
from Umm Salama, who said: "I never saw the Messenger of Allah, peace and blessings be upon him, fast two consecutive months, except that he would join Sha'ban to Ramadan." (2)

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= Hayyan — so another narrated it — as will come — from Muhammad ibn 'Amr, from Yahya ibn Abi Kathir, from Abu Salama, from Abu Hurayra. Al-Mizzi said in "Al-Tuhfa" (6564): And it is the preserved [version].
Ahmad also narrated it (9654) from Yahya al-Qattan, and (10451) from Muhammad ibn 'Abd Allah al-Ansari, and al-Tirmidhi (684) via the route of 'Abda ibn Sulayman — all three of them from Muhammad ibn 'Amr, from Yahya ibn Abi Kathir, from Abu Salama, from Abu Hurayra, raised [to the Prophet].
And it has preceded in the usual manner in the two previous narrations.

(1) In (M): "therein" instead of "concerning that."
(2) Its chain is sound. 'Abd al-Rahman: he is Ibn Mahdi, and Sufyan: he is Ibn Sa'id al-Thawri, and Mansur: he is Ibn al-Mu'tamir, and Salim: he is Ibn Abi al-Ja'd, and Abu Salama: he is Ibn 'Abd al-Rahman ibn 'Awf. It is in "Al-Sunan al-Kubra" under number (2496).
Al-Tirmidhi also narrated it in his "Sunan" (736), and in "Al-Shama'il" (295) from Muhammad ibn Bashshar, with this chain. He said in "Al-Sunan": A hasan hadith. And he said in "Al-Shama'il": This is a sound chain, and this hadith has been narrated by more than one from Abu Salama, from 'A'isha, from the Prophet, peace and blessings be upon him, and it is possible that Abu Salama ibn 'Abd al-Rahman narrated this hadith from both 'A'isha and Umm Salama, from the Prophet, peace and blessings be upon him.
Ahmad also narrated it (26562) from 'Abd al-Rahman ibn Mahdi, with it.
And he narrated it — abbreviated — Ahmad (26517) via the route of al-Jarrah ibn Mulayh, and Ibn Majah (1648) via the route of Shu'ba, both of them from Mansur with it. The wording of Ahmad is: "He used to fast Sha'ban and Ramadan." And the wording of Ibn Majah is: "He used to join Sha'ban to Ramadan."