A more thorough explanation:

Definition: Earnest-penny, also known as God's penny or denarius Dei, is a small sum of money paid by a buyer to a seller as a sign of good faith and commitment to a contract of sale. It is a historical term that was commonly used among merchants in Western Europe.

Example: In medieval times, a buyer who wanted to purchase a horse from a seller would give an earnest-penny to the seller as a sign of commitment to the sale. The seller would then accept the earnest-penny and agree to sell the horse to the buyer at the agreed-upon price.

Explanation: The example illustrates how an earnest-penny was used as a form of security in a contract of sale. By giving the seller an earnest-penny, the buyer showed that they were serious about the purchase and committed to following through with the sale. The seller, in turn, accepted the earnest-penny as a sign of good faith and agreed to sell the item to the buyer. This helped to establish trust between the two parties and ensured that the sale would be completed as agreed.