  The \hi 21 cm transition line is expected to be an important probe into the
cosmic dark ages and epoch of reionization. Foreground source removal is one of
the principal challenges for the detection of this signal. This paper
investigates the extragalactic point source contamination and how accurately
bright sources ($\gtrsim 1$ ~Jy) must be removed in order to detect 21 cm
emission with upcoming radio telescopes such as the Murchison Widefield Array
(MWA). We consider the residual contamination in 21 cm maps and power spectra
due to position errors in the sky-model for bright sources, as well as
frequency independent calibration errors. We find that a source position
accuracy of 0.1 arcsec will suffice for detection of the \hi power spectrum.
For calibration errors, 0.05 % accuracy in antenna gain amplitude is required
in order to detect the cosmic signal. Both sources of subtraction error produce
residuals that are localized to small angular scales, $\kperp \gtrsim 0.05
$Mpc$^{-1}$, in the two-dimensional power spectrum.
