No one can change his purpose to the injury of another.

Explanation

A man may not reverse his course of action when doing so would injure another who has relied upon his original undertaking — change of mind does not excuse the harm it causes.

Where this applies

• A contractor agrees to build a house with south-facing windows so the neighbor can maintain his solar panels, then mid-construction switches to north-facing windows — the contractor cannot change his plan to the injury of the neighbor who relied on the original design.
• A landlord promises a tenant a one-year lease and the tenant moves across the country to take the apartment, then the landlord changes his mind and rents to someone else — the landlord may not reverse course when doing so injures someone who relied on his commitment.
• A business partner agrees to a profit-sharing arrangement and the other partner invests heavily based on that agreement, then the first partner unilaterally changes the terms — changing purpose after another has relied on your word to their detriment is not permitted.