Dear …
RE: Job Offer - __(Name of Position)__
Thank you so much for offering to me, the position of __(type of position)__ with __(name of company)__.
I was fortunate to have received another very impressive job offer from my previous employer and over the last few days I have been left with making the very difficult decision of choosing the organization and the position that best meets my needs. After lengthy consideration, I have decided to accept the offer presented to me by my previous employer. I believe that they are offering the best combination of __(list a couple type of benefits: i.e. remuneration package/time schedules/shorter commuting distance for me)__.
Thank you for taking the time to interview me. I appreciate your offer and ask that you kindly hold my resume on file should there ever be need for future consideration.
Sincerely,