2,355. Beginning Basar b'Chalav

Maachalos Assuros 8:18

The general rule is that when something is prohibited under Biblical law, one may not do business with it. When something is prohibited rabbinically, one is permitted do business with it regardless of whether the presence of the prohibited thing is sure or in doubt.

Maachalos Assuros 9:1

It is prohibited under Biblical law to cook meat and milk together and to eat them. It is likewise prohibited to benefit from it. Such a mixture must be buried, and its ashes are prohibited like the ashes of all things that must be buried. If someone cooks an olive-sized portion of these two things together, he is liable to lashes as per Exodus 23:19, “Do not cook a kid in its mother’s milk.” Similarly, one who eats an olive-sized portion of meat and milk that were cooked together is liable to lashes even if he wasn’t the one who cooked them.