On the retirement of an existing partner, an increase in the value of a liability will be credited to :-

When a liability increases, the liability account is credited, and the Revaluation Account (also known as Profit and Loss Adjustment Account) is debited.The journal entry is:
$$\text{Revaluation A/c (or P\&L Adjustment A/c)}\text{Dr.}$$
$$\text{To Liability A/c}$$
Hence, the increase in the value of a liability is credited to the Liability Account.