To what extent is it lawful to obligate the buyer to pay the price of a sheep he bought "verbally" that died while still with the seller before payment or delivery, and is he sinful if he does not pay?

If a contract is made for a sheep and you leave it as a trust with the seller, and the agreement concludes, then the sale is valid, and its ownership transfers to you, and you are obligated to pay its price, even if you do not pay the price immediately. If the sheep perishes while with the seller, without any negligence on his part, then its misfortune is upon you, and you are obligated to pay its price, provided that there is evidence of its perishing. Otherwise, you are not obligated to guarantee it.