Dear Mr. George,
I have your letter dated 01 Jan 2xxx. Thank you very much for your offer of a job as SECURITY OFFICER in your firm. However, I regret to inform you that I am unable to accept your offer. The reason is that my family has objected to the idea of me being an armed guard. They figured that it is too great a burden for a man my age.
I have secured another job as a watchman for a factory in Singapore. The job is fairly easy and less risky. Also I can be with my family here.
I appreciate your offer but I am sure you can find someone better and younger to serve in your company. Thank you.