Musannaf Ibn Abi Shayba 9:1454

Ibn Idris narrated to us, from Hisham, from Ibn Sirin, who said: The milk of the stud (male animal) was mentioned, and he said: Some people disliked it, and some people permitted it. Those who disliked it were considered better in the view of the people, and al-Qasim ibn Muhammad was among those who disliked it.