The Messenger of Allah ﷺ would recite a verse of prostration outside of formal prayer, then he would prostrate and we would prostrate along with him, until at times one of us could not find a spot to place his forehead in prostration.
حدثنا ابن نمير حدثنا عبيد الله عن نافع
أن رسول الله ﷺ كان يصلي يعني يقرأ السجدة في غير صلاة فيسجد ونسجد معه حتى ربما لم يجد أحدنا مكانا يسجد فيه
Its isnad is sahih. This is the fuller version of 4669, and that one comes from the narration of Yahya Qattan from Ubaydullah, with the wording, "He would recite the surah to us, and when he recited a sajdah verse he would prostrate and we would prostrate with him," and so on, without mentioning that this happened outside of prayer.Bukhari narrated it likewise, 2:459, 462, with two chains through Yahya, and 2:459 through Ali bin Mushir, both of them from Ubaydullah, without mentioning that it was outside of prayer. Muslim likewise narrated it, 1:161, through Yahya from Ubaydullah, without this addition, then he narrated it through Muhammad bin Bishr from Ubaydullah, adding at the end, "outside of prayer."This shows that this addition is established from the narration of Ibn Numayr here and Muhammad bin Bishr with Muslim, both of them from Ubaydullah. The wording found here is the one established in H and K. In M it reads, "He used to pray," meaning he would recite the sajdah verse and prostrate, and so on, without mentioning "outside of prayer" in it. In its margin there is another version, "He used to recite Surat Sajdah outside of prayer, then prostrate," and so on.I hold that what is in H and K is the correct version, since both agree on it, and because it matches in meaning the narration of Muslim through Muhammad bin Bishr.