employee-rescinding-verbal-resignation

Hello, we have an employee who verbally told his manager that he is pursing a new job and is resigning. Fast forward a few weeks later he has indicated that the offer from the prospective new employer was not to his satisfaction and that he now is planning on staying. In the interim he has told all of his peers that he is leaving and has had a detrimental impact on morale. What are the ramifications now if his employment is terminated?