What is the ruling on the suckling of an adult? Is it forbidden, permissible, or recommended? What is its nature? Should it be done directly or through a vessel? Should a female servant be suckled to become a mahram?

The preponderant opinion is that adult suckling does not establish a prohibitive degree of kinship (mahramiyyah), and this is the view of the majority of scholars and the four imams. The incident of Salim, the mawla of Abu Hudhayfah, was to address a specific circumstance related to adoption before Islam, and this circumstance is not repeatable. Therefore, it is not permissible for an adult to suckle from a maid or anyone else, and no mahramiyyah results from it. The manner of his suckling was by drinking the expressed milk from a vessel, not directly from the breast.