I'tikaf

Sayyiduna Anas bin Malik (may Allah be pleased with him) says that the Messenger of Allah (peace and blessings be upon him) used to observe i'tikaf in the last ten days of Ramadan. One year he (peace and blessings be upon him) was unable to observe i'tikaf, so when the following year came he (peace and blessings be upon him) observed i'tikaf for twenty days.
This hadith is sahih (authentic) on the condition of the two Shaykhs (Bukhari and Muslim), and they did not record it.

It is narrated from Sayyiduna Ubayy bin Ka'b (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) used to observe i'tikaf in the last ten days of Ramadan. One year he (peace and blessings be upon him) travelled and so could not observe i'tikaf; then the following year he (peace and blessings be upon him) observed i'tikaf for twenty nights.

It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) said: "Fasting is not obligatory upon the one in i'tikaf (merely because of the i'tikaf), unless he makes it binding upon himself (by a vow)."
The chain of this hadith is sahih (authentic) on the condition of Imam Muslim, but the two Shaykhs did not record it. Although the jurists of Kufa have narrated two hadiths to the contrary, which I shall mention, they cannot match this report by the measure of the narrators' integrity.

It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that Sayyiduna Umar (may Allah be pleased with him) had vowed in the Days of Ignorance (Jahiliyyah) to observe i'tikaf for one day. He then asked the Prophet (peace and blessings be upon him) about it, and he (peace and blessings be upon him) said: "Complete your i'tikaf, and fast that day as well."

It is narrated from Sayyidah Aishah (may Allah be pleased with her) that the Prophet of Allah (peace and blessings be upon him) said: "There is no (valid) i'tikaf without fasting."
Imam Bukhari and Imam Muslim did not use Sufyan bin Husayn and Abdullah bin Budayl as evidence.

Sayyiduna Ibn Abbas (may Allah be pleased with them both), in explaining the saying of Allah Almighty: "And upon those who are able to do it (but do not fast), a ransom: the feeding of one poor person" [Surah al-Baqarah: 184], said: whoever willingly adds to the good, "And whoever does good voluntarily", feeds one more poor person, "it is better for him." He said that this verse is not abrogated; rather, it applies to the elderly man who is unable to fast: he was commanded to feed (as a ransom) when he knows that he is unable to fast.
This hadith is sahih (authentic) on the condition of the two Shaykhs (Bukhari and Muslim), and they did not record it.

It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the very elderly man was given the concession not to fast and to feed one poor person for each day, and no making up (qada) of the fasts is due from him.
This hadith is sahih (authentic) on the condition of Imam Bukhari, and they did not record it.