Prescription and execution do not pertain to the validity of the contract, but to the time and manner of bringing the action.

Explanation

The statute of limitations and the mode of enforcement affect only procedure, not the underlying validity of the contract — a barred action does not mean the obligation never existed.

Where this applies

• A debtor repays a ten-year-old loan even though the statute of limitations has expired — the lender can keep the money because the underlying debt was always valid, just procedurally unenforceable.
• A contractor's breach-of-contract claim is dismissed as time-barred, but that doesn't mean the contract was never valid — it only means the window to sue has closed.
• A borrower argues the expired limitations period proves the loan never existed; the court corrects him — prescription affects the remedy, not the obligation itself.