The ruling on selling birds in the air and selling wool on the back

Question:
Honorable Shaykh, may Allah grant you success, what is your opinion on this statement, and is it correct that it is valid to sell birds in the air if they are accustomed to returning, so that if they return, well and good, but if not, the buyer has the right to open the cage?

Answer:
No, it is not permissible, even if they are accustomed to returning, because they may not return. However, they say that if the bird flies but is in an enclosed place, like a room or a location where it cannot be obtained because it has no way to escape, that is different. But if it is in the air and not in an enclosure, this is not permissible, even if it is accustomed to returning. As for the one who says it is permissible to sell wool on the back, that is because the wool is visible and known, but the Prophet (peace and blessings be upon him) prohibited selling wool on the back. This is because there is disagreement between them regarding the amount of the portion, yes, and because the wool is a part of the animal, and it is alive. As for if it is being slaughtered.