If there is uncertainty about whether breast-feeding took place, or about the exact number of nursings, the ruling is based on what is certain.

Should a reliable wet nurse testify that the breast-feeding occurred, the resulting prohibition is established.

Any woman whose daughter a man may never marry—such as his mother, grandmother, or sister—if she suckles a young girl, that girl becomes permanently unlawful for him.

Likewise, any man whose daughter is forbidden to another—such as his father, grandfather, brother, or son—if that man’s wife breast-feeds a young girl with his milk, that girl is forever forbidden to the other man.