Dear (person),
Thank you very much for responding to our advertisement for a (thing) for the (place or idea). We have been very pleased that many qualified individuals have applied for this position, but it has also made the selection process difficult.
Although we cannot offer you a position in our organization at this time, we will keep your resume on file for future reference.
Thank you once again for applying to our organization. We wish you the best of luck in your future endeavors.
Sincerely,