Muhammad bin Isma'il bin Samra محمد بن إسماعيل بن سمره الأحمسي · Chapters on Slaughtering

“Avoid those that are lactating.” (i.e. those from which milk is received).

“Let us go out to Waqifi.” He said: “So we went out in the moonlight until we came to the garden and he (the owner of the garden) said: ‘Welcome.’ Then he took up the knife and went among the sheep (to choose one for slaughter), and the Messenger of Allah (ﷺ) said: ‘Avoid those that are lactating.’”