Sahih al-Bukhari Book 33, Hadith 11
I asked Abu Sa`id Al-Khudri, "Did you hear Allah's Messenger (ﷺ) talking about the Night of Qadr?" He
replied in the affirmative and said, "Once we were in I`tikaf with Allah's Messenger (ﷺ) in the middle ten
days of (Ramadan) and we came out of it in the morning of the twentieth, and Allah's Messenger (ﷺ)delivered
a sermon on the 20th (of Ramadan) and said, 'I was informed (of the date) of the Night of
Qadr (in my dream) but had forgotten it. So, look for it in the odd nights of the last ten nights of the
month of Ramadan. I saw myself prostrating in mud and water on that night (as a sign of the Night of
Qadr). So, whoever had been in I`tikaf with Allah's Messenger (ﷺ) should return for it.' The people returned
to the mosque (for I`tikaf). There was no trace of clouds in the sky. But all of a sudden a cloud came
and it rained. Then the prayer was established (they stood for the prayer) and Allah's Messenger (ﷺ)
prostrated in mud and water and I saw mud over the forehead and the nose of the Prophet.
Safiya, the wife of the Prophet (ﷺ) told me that she went to Allah's Messenger (ﷺ) to visit him in the mosque while he was in I`tikaf in the last ten days of Ramadan. She had a talk with him for a while, then she got up in order to return home. The Prophet (ﷺ) accompanied her. When they reached the gate of the mosque, opposite the door of Um-Salama, two Ansari men were passing by and they greeted Allah's Apostle . He told them: Do not run away! And said, "She is (my wife) Safiya bint Huyai." Both of them said, "Subhan Allah, (How dare we think of any evil) O Allah's Messenger (ﷺ)!" And they felt it. The Prophet said (to them), "Satan reaches everywhere in the human body as blood reaches in it, (everywhere in one's body). I was afraid lest Satan might insert an evil thought in your minds."
One of the wives of Allah's Messenger (ﷺ) practiced I`tikaf with him while she ad bleeding in between her periods and she would see red (blood) or yellowish traces, and sometimes we put a tray beneath her when she offered the prayer.