Is it permissible for the buyer to reclaim the amount paid to the seller, and what is the ruling on the sale, if the animal dies after the buyer left it with the seller for a week and the seller had received part of the price?

If the animal perishes while with the seller after the buyer has taken possession of it, and it was with the seller as a trust (wadi'ah) or a pledge (rahn) without any transgression on his part, then there is no liability upon him, and it is under the buyer's guarantee. However, if it perishes before possession is taken, the buyer is entitled to reclaim the price he paid to the seller.