We report three-dimensional simulations of the reversible reaction A+B <---->C for a single static A molecule and a uniform initial concentration of noninteracting B-molecules. The results are compared with various analytic approximations for the time-dependence of the binding probability. They are in excellent agreement with a recent theory of Sung and Lee [J. Chem. Phys. 111, 796 (1999)] for all times and rate parameters. The second-order term in the long-time expansion of this theory is incorrect, yet it explains an apparent kinetic transition observed when the B-concentration increases. We also investigate the concentration profiles near the reversible trap.