What is the authenticity of what is stated in Malik's Muwatta (Book of Suckling), Chapter: What Has Been Said About Suckling After Reaching Adulthood, especially that which is understood to concern Aisha?

The aforementioned hadith (definition) is authentic, and its origin is found in the two Sahih (definition) collections and others. Imam Malik mentioned it to clarify the Islamic ruling on breastfeeding in adulthood. The majority of scholars among the Companions, including Umar, Ibn Mas'ud, and Umm Salamah, hold the view that breastfeeding only establishes prohibition if it occurs within the first two years of life, and that the story of Sahlah is specific to her. As for Aisha, may Allah be pleased with her, her view was that adult breastfeeding establishes prohibition, citing the aforementioned hadith as evidence. However, the established doctrines of the Sunni schools of thought are that adult breastfeeding does not establish prohibition. The statement by Aisha, may Allah be pleased with her, that she used to instruct her sister or her nephews' daughters to breastfeed men whom she wished to enter upon her, means that, in her view, adult breastfeeding establishes prohibition. Consequently, this man would become her sister's son through fosterage and thus a mahram (definition) to her, as breastfeeding establishes the same prohibitions as birth.