What is the ruling on slaughtering a sheep then buying its meat, head, and hide, and leaving the rest of its parts?

Vagrant thoughts are not held against a person. However, if you vocalize them and intend them as a vow, then you are obliged to fulfill it according to what you intended. If you intended to give away lamb meat as charity, that suffices. But if you intended to buy and slaughter it, then your obligation is not discharged except by slaughtering it. This type of vow is disliked.