A more thorough explanation:

Sacramentum decisionis (sak-rə-men-təm di-sizh-ee-oh-nis) is a Latin term used in civil law. It refers to the offer made by one party in a lawsuit to accept the opposing party's oath as decisive of the issues involved in the case. This means that the party making the offer believes that the opposing party's oath will settle the matter at hand.

One example of sacramentum decisionis is when a defendant or person accused of a crime is asked to make an oath of their own innocence. They may also be required to produce a certain number of compurgators, who swear that they believe the defendant's oath. This is similar to the sacramentum decisionis because it involves an oath being used to settle a legal matter.

Another example of sacramentum decisionis is when one party in a lawsuit is unable to prove their charge. In this case, they may offer to refer the decision of the case to the oath of their adversary. The adversary is then bound to accept the offer or tender the same proposal back again. If they do not accept the offer, the whole matter is taken as confessed by them.

The examples illustrate how sacramentum decisionis is used in civil law to settle legal matters. In both cases, an oath is used to determine the outcome of a lawsuit. The party making the offer believes that the opposing party's oath will be decisive in settling the matter at hand. If the offer is accepted, the case is settled based on the oath. If it is not accepted, the matter is taken as confessed by the party who refused the offer.