What is the ruling on selling live animals (such as cattle, sheep, and poultry) to a non-Kitabi disbeliever who slaughters them in a non-Islamic manner for consumption by non-Muslims, and are there any other proofs besides what Ibn Hajar al-Haytami mentioned regarding the prohibition of selling if the seller knows that the buyer will use the sold item in a forbidden way?

It is forbidden to sell musk to a disbeliever when it is known that he will use it to perfume an idol, just as it is forbidden to sell an animal to a belligerent when it is known that he will kill it without proper slaughter. This is because anything that the seller knows the buyer will use to commit a sin is forbidden for him to sell to him. Disbelievers are bound by the branches of Islamic law, and the two mentioned sins are grave. Therefore, assisting in them is not permissible, whether based on certain knowledge or strong presumption.