The Shaykh’s explanation of the hadith of Ibn 'Abbas (may Allah be pleased with him and him) that the Messenger of Allah (peace and blessings be upon him) entered upon 'Umar while he was on a mat that had left a mark on his side, and he said

The Shaykh : The hadith that follows it, which is also authentic, is his statement regarding Ibn 'Abbas (may Allah be pleased with him and him) that the Messenger of Allah (peace and blessings be upon him and his family) entered upon 'Umar while he was on a mat that had left a mark on his side, and he said “O Messenger of Allah, if only you would take a mattress more comfortable than this”. He said It was narrated by Ahmad, Ibn Hibban in his Sahih, and al-Bayhaqi.
Similar to what was mentioned before is his statement, and from him, meaning Ibn 'Abbas, he said: 'Umar ibn al-Khattab narrated to me, saying: I entered upon the Messenger of Allah (peace and blessings be upon him and his family) while he was on a mat. He said “So I sat down, and I saw that he had only his izar on, and nothing else”. The izar is the garment that covers the lower part of the body, and the rida' covers the upper part of the body. So this is part of what the narrator describes regarding the Messenger (peace be upon him): when he entered upon him, he had no clothing on except the izar that covered his 'awrah (peace and blessings be upon him). Then he describes the house or room in which he was, and the mat on which he was sitting. He said: So I sat down, and I saw that he had only his izar on, and nothing else. And I saw that the mat had left a mark on his side. And I saw a handful of barley, about a sa' (a dry measure of about 3 kg), and some tamarisk in a corner of the room. This is all the provision found in the house of the Messenger of Allah (peace and blessings be upon him and his family); it is nothing but the mat, the handful of barley, and a little tamarisk with which they used to anoint the ahyab, meaning skins, before tanning them. And tamarisk in a corner of the room. And I saw an ahyab hanging, as if this tamarisk was prepared to tan this ahyab. And I saw an ahyab hanging. Then my eyes burst into tears, meaning 'Umar ibn al-Khattab (may Allah be pleased with him) was weeping. He said He said “O Prophet of Allah, why should I not weep? This mat has left a mark on your side, and this is your storehouse; I see nothing in it but what I see of barley and tamarisk. And there is Kisra and Caesar in fruits and rivers, and you are the Prophet of Allah and His chosen one”. And this is your storehouse; why should I not weep? You are the master of mankind, and you are in this poverty, while those disbelievers, the kings of Kisra and Caesar, live in luxury, in silk, and in rivers. He said The hadith ends here in this book. However, it must be supplemented with the addition of Ibn Majah. I said: Yes, this addition is not found in the book here in this copy, so it should be supplemented for those who have a copy like mine. He said I said “Yes”. It was narrated by Ibn Majah with a sound chain, and by al-Hakim, who said it is authentic according to the conditions of Muslim. There is a correction here regarding this attribution. I said: And in his correction regarding Muslim, there is an error, and in the author’s attribution to Ibn Majah, there is a shortcoming. For Muslim narrated it in the fourth part, on pages 188 to 189, in the story of his (peace and blessings be upon him) seclusion from his wives, with the wording of Ibn Majah, and his chain up to the end of the commentary. So the author attributed it only to Ibn Majah, then to al-Hakim, and mentioned that al-Hakim authenticated it according to the conditions of Muslim. Here there is an error on the part of al-Hakim and a shortcoming on the part of the author. The error on the part of al-Hakim is that he extracted this hadith in his book al-Mustadrak and said it is authentic according to the conditions of Muslim. He only extracts in that book what did not come in Sahih al-Bukhari or Sahih Muslim, and the hadith is according to their conditions or the condition of one of them. In this case, he cites the hadith and says it is authentic according to the conditions of al-Bukhari or authentic according to the conditions of Muslim. So al-Hakim supplemented this hadith and said its chain is authentic according to the conditions of Muslim, and he missed that Imam Muslim narrated it as al-Hakim did in his Sahih. From this, the shortcoming of the author becomes clear, where he limited the attribution of the hadith to Ibn Majah and al-Hakim, whereas it was more appropriate to attribute it to Sahih Muslim. But after the narrator moved away from the likely source, the author was further removed from recalling his attribution to Sahih Muslim, because Muslim only narrated this portion in the context of his (peace be upon him) seclusion from his wives in a well-known story that Muslim narrated in its entirety. In its details, when 'Umar ibn al-Khattab heard that the Prophet (may the prayers and peace of Allah be upon him) had secluded himself from his wives, he came to him to console him (peace be upon him) or to help him with what he was going through. When he entered upon him, he saw what came in this narration. So in this story in its entirety, this portion of it came in the Sahih. Neither al-Hakim nor the author noticed this. And this happens to every author, for infallibility belongs to Allah alone (Glorified and Exalted is He).