The Messenger of Allah ﷺ drank some milk, then prayed without rinsing his mouth or performing ablution.
إن رسول الله ﷺ شرب لبنا فلم يمضمض، ولم يتوضأ وصلى.
Abu Dawud reported it (197). He said, Uthman bin Abu Shayba told us, from Zayd bin Hubab, from Muti bin Rashid, from Tawba Anbari, that he heard Anas bin Malik, and he mentioned it. Zayd said, "Shuba directed me to this shaykh." Its isnad is hasan because of Muti bin Rashid, for no one confirmed his reliability except Shuba, according to what Zayd bin Hubab said about being directed to him. Had Shuba not known him, he would not have directed Zayd to him, and had he known of any criticism against him, he would have mentioned it. Abu Dawud said, as recorded in Tahdhib al-Tahdhib, "Shuba praised him." This removes the charge of him being unknown, since only Zayd bin Hubab narrated from him. Hafiz graded its isnad hasan in Fath al-Bari (1/313) and said, "Ibn Shahin made a strange claim when he treated the hadith of Anas as abrogating the hadith of Ibn Abbas, without mentioning who held the view of obligation that would necessitate a claim of abrogation." End of quote.As for what Ibn Majah reported (501) from Ishaq bin Ibrahim Sawwaq, who said, Dahhak bin Makhlad told us, who said, Zama bin Salih told us, from Ibn Shihab, from Anas bin Malik, who said, "The Messenger of Allah milked a ewe and drank from its milk, then called for water and rinsed his mouth, saying, 'It has fat in it,'" this is daif, because of Zama bin Salih Jundi Yamani, a resident of Makkah. The scholars are unanimous in declaring him daif. Bukhari said, "He contradicts others in his hadith." Ibn Hibban said, "He was a righteous man who made mistakes without realizing it and erred without understanding, until his hadith became overwhelmed with objectionable narrations that he related from well-known narrators." For this reason Mizzi said in Tuhfat Ashraf (1/378), "More than one narrator reported it from Zuhri, from Ubaydullah bin Abdullah bin Utba, from Ibn Abbas, and that is the preserved version." End of quote.I say, likewise, what is reported from Umm Salama is not valid, that she said, the Messenger of Allah ﷺ said, "When you drink milk, rinse your mouths, for it contains fat." Ibn Majah reported it (499). He said, Abu Bakr bin Abu Shayba told us, Khalid bin Mukhlad told us, from Musa bin Yaqub, Abu Ubayda bin Abdullah bin Zama told me, from his father, from Umm Salama.Khalid bin Mukhlad Qatwani was truthful in himself, but he was criticized for holding Shia sympathies. Musa bin Yaqub Mutalibi Zamai is disputed. Ibn Main confirmed his reliability. Abu Dawud said, "Salih." Ibn Adi said, "In my view, there is no harm in him." Ibn Hibban listed him among the reliable narrators. Ibn Madini declared him daif and said, "Daif, with objectionable hadith." Nasai said, "He is not strong." Ahmad said, "His hadith does not please me." The summary regarding him, as Hafiz said, is "Truthful but with poor memory." Someone like this cannot have his hadith accepted when he narrates something alone or contradicts others, and here he alone narrated the wording as a command, while the correct version is that it was an action of the Prophet ﷺ.As for Busiri's statement, "His narrators are reliable," this is not to be taken as absolute.On this subject there is also what is reported from Abdul-Muhaymin bin Abbas bin Sahl bin Saad Saadi, from his father, from his grandfather, that the Messenger of Allah ﷺ said, "Rinse your mouths after milk, for it has fat in it." Ibn Majah reported it (500) from Abu Musab, who said, Abdul-Muhaymin bin Abbas told us, with his isnad. Its isnad is daif because of this Abdul-Muhaymin, for the scholars are unanimous in declaring him daif, and Busiri criticized it on this basis in Zawaid, saying, "This isnad is daif. Abdul-Muhaymin, Bukhari said, has objectionable hadith."