When Uthman bin Mazun died, his bier was carried out and he was buried. The Prophet ﷺ ordered a man to bring him a stone, but the man was unable to lift it. So the Messenger of Allah ﷺ went over to it himself and rolled up his sleeves.Kathir said that Muttalib reported that the one who related this to him from the Messenger of Allah ﷺ said, "It is as if I can still see the whiteness of the Messenger of Allah's ﷺ forearms when he uncovered them."He then carried the stone and placed it at the head of the grave, saying, "I am marking my brother's grave with it, so I may bury beside him whoever dies from my family."
لما مات عثمان بن مظعون أخرج، بجنازته، فدفن، فأمر النبي ﷺ رجلا أن يأتيه بحجر، فلم يستطع حمله، فقام إليها رسول الله ﷺ و حسر عن ذراعيه، قال كثير: قال المطلب: قال الذي يخبرني ذلك عن رسول الله ﷺ قال: كأني أنظر إلى بياض ذراعي رسول الله ﷺ حين حسر عنهما، ثم حملها فوضعها عند رأسه وقال: أتعلم بها قبر أخي، وأدفن إليه من مات من أهلي.
Abu Dawud reported it (3206) through two routes from Kathir bin Zayd Madani, from Muttalib, and he mentioned it. Kathir bin Zayd is disputed, but his hadith is hasan. Hafiz said in Talkhis (1332), "Its isnad is hasan, there is nothing in it except Kathir bin Zayd, who narrates it from Muttalib, and he is truthful. Muttalib made clear that an informant told him this without naming him, and the anonymity of the companion does not cause harm."As for what is narrated from Anas bin Malik that the Messenger of Allah ﷺ marked the grave of Uthman bin Mazun with a rock, this is an error. Ibn Majah reported it (1561) through another route from Kathir bin Zayd, from Zaynab bint Nubayt, from Anas. Hafiz said in Talkhis (2/133-134), "Abu Zura said, 'This is an error,' and indicated that the correct version is the narration of those who reported it from Kathir from Muttalib." He also said, "Tabarani reported it in Awsat from the hadith of Anas with another isnad that contains weakness, and Hakim reported it in Mustadrak, in the biography of Uthman bin Mazun, with another isnad containing Waqidi, from the hadith of Abu Rafi, and he mentioned its meaning." End of quote.Likewise, what is narrated from Abdullah bin Muhammad bin Umar, from his father, that the Messenger of Allah ﷺ sprinkled water on the grave of his son Ibrahim, is not sound. Ibn Umar added in his narration that it was the first grave that water was sprinkled on, and that when he was buried and the burial was finished, he said at his head, "Peace be upon you," and I know of nothing else except that he said he scattered soil on it with his hand. Qanabi did not say "Ibn Umar."Abu Dawud reported it in Marasil (414) from Abdullah bin Maslama bin Qanab, and Abdullah bin Umar bin Muhammad bin Abu Aban bin Salih, that Abdul-Aziz bin Muhammad narrated to them, from Abdullah bin Muhammad bin Umar, from his father, and he mentioned it. Abdullah bin Muhammad bin Umar is Ibn Ali bin Abu Talib, Abu Muhammad, Alawi, Madani. Hafiz said of him, "acceptable," meaning when corroborated, and he was not corroborated, so his hadith is weak. His father, Muhammad bin Umar bin Ali bin Abu Talib, is truthful, and his narration from the Messenger of Allah ﷺ is mursal.Likewise, what Shafii reported in his Musnad (360), and from him Bayhaqi (3/411), from Ibrahim bin Muhammad, from Jafar bin Muhammad, from his father, that the Prophet ﷺ sprinkled water on the grave of his son Ibrahim and placed pebbles on it, is not sound. Shafii said, "Pebbles are not placed except on a flattened grave." End of quote. Ibrahim bin Muhammad is Ibn Abu Yahya, Aslami, who is accused of fabrication, along with the mursal nature of the chain.Likewise, sprinkling water on the grave of the Prophet ﷺ is not established. Bayhaqi reported it from the hadith of Jabir, and the one who sprinkled it was Bilal bin Rabah, who began from the side of his head, from his right side, until he finished at his feet. Its isnad contains Waqidi, as Hafiz stated in Talkhis (2/133), and there is another hadith on this matter, except that it is mursal.