He Sees You When You're Sleeping by Mary Higgins Clark and Carol Higgins Clark was published in 2001.
Mary Higgins Clark - He Sees You When You're Sleeping book description:
Sterling Brooks has been cooling his heels in the Celestial Waiting Room for forty-six years, waiting for admission to heaven. Finally, just days before Christmas, he’s summoned before the Heavenly Council and found unworthy; throughout his life he had been hopelessly self-absorbed. To redeem himself, he is given the chance to go back to Earth and find someone to help.
At New York’s Rockefeller Center skating rink, Sterling encounters Marissa, a heartbroken seven-year-old whose father and grandmother have been forced into the Witness Protection Program; they had overheard two gangsters hatch a sinister plot to collect money from a debtor.
Able to travel through time and space, Sterling devises a master plan to reunite little Marissa with her family in time for Christmas. Along the way, he discovers within himself what it takes to earn his wings.