delivered the opinion of the court.

There was no subrogation here, legal or conventional. One who discharges for the debtor to the creditor, who holds an incumbrance or lien securing the debt, such debt, by agreement express or reasonably inferable from the facts of the particular case, that he shall have the incumbrance or lien kept alive for his benefit, is protected within the rule for conventional subro*95gation. In such case there is an agreement, equally whether it be express or so implied, and the agreement is for, and secures, subrogation. One who discharges to the creditor holding such lien or incumbrance, -the debt, when he is, himself, under some legal obligation to pay the debt, is protected within the rule for legal subrogation, quite independently of agreement, express or implied. But he who discharges to the creditor holding such lien or incumbrance, a debt of the debtor, under circumstances making him a prime volunteer, is not entitled to subrogation. Mere payment, in and of itself, never entitles to subrogation, and appellant’s case rests on mere payment alone. Here a note was taken for the money loaned from the debtor, with no agreement, express or reasonably inferable from the facts, that the trust deed should be kept alive for the security of the lender, who was under no legal obligation to pay, and who paid only a part of the secured debt. Staples v. Fox, 45 Miss., 681; Howell v. Bush, 54 Miss., 445; White v. Cannon, 125 Ill., 412; Sheldon on Subrogation, §§ 3, 241, 240, 245, 246. It makes no difference that the money is loaned to pay off a lien, if that bare fact be all. Sheldon on Subrogation, §243; Gardenville Association v. Walker, 52 Md., 452. The reason why one who has innocently acquired an invalid title at a sale is subrogated to the rights of him to whom his money has been paid, is, as very correctly put by counsel for appellee, “that the payee has not knowingly undertaken the risk of his payment of the incumbrance, lien, or purchase money. ’ ’

In Chaffe v. Patterson, 61 Miss., 28, there was no appeal by Mrs. Henry from the decree of the chancellor in the litigation between her and John Chaffe & Sons holding Chaffe & Sons entitled to subrogation to the rights of her vendor against the Montgomery lands. That holding was clearly erroneous, and would have been reversed on appeal. But it stood unreversed, and so was the law of that particular case; and Patterson et al., in their litigation with Chaffe & Sons, were affected with notice *96that it was the law of that case, the decree standing unreversed and unappealed from. And that is all that is held in that case. The decree is correct, and it is

Affirmed.