Draft for Employee Retention Letter for notice period?

Dear Members,
I would be needing a employee retention letter. The background is : we have terminated the employee and he is on notice. Now we would like to retain him on a notice period of 3 months.
Please help with sharing the draft letter.
Thanks & Regards,
Rinki

Dear Rinki,
Rather than issuing the letter directly, it is better if employee puts up application for the extension of the notice period. Get approval from the management and issue letter stating that his request has been approved and his notice period is extended up to ______ (date). Notwithstanding the extension of notice period, there will not be any change in the other terms and conditions of his employment.
Thanks,
Dinesh Divekar

Dear Dinesh,
Thanks for the advise. I think it makes sense.
Many thanks...much appreciated!
Regards,
Rinki