If his oath would change his obligation from one liability to another, such as that the ox he borrowed died naturally, when actually it was captured, and in both of which cases he would be liable to pay, his oath changes nothing. If he confesses that he swore falsely, he does not have to bring the usual sacrifice nor pay one-fifth extra. The same would apply if he swore to change from one exemption to another, or from an exemption to a liability.
However, if he swears to change from liability to exemption but then confesses, he needs to bring a guilt offering and must add one-fifth to the amount.
Art: Oxen on the beach by Joaquin Sorolla y Bastida