  A key to understanding the formation of the first galaxies is to quantify the
content of the molecular gas as the fuel for star formation activity through
the epoch of reionization. In this paper, we use the 158$\mu$m [CII]
fine-structure emission line as a tracer of the molecular gas in the
interstellar medium (ISM) in a sample of $z=6.5-7.5$ galaxies recently unveiled
by the Reionization Era Bright Line Emission Survey, REBELS, with the Atacama
Large Millimeter/submillimeter Array. We find substantial amounts of molecular
gas ($\sim10^{10.5}\ M_\odot$) comparable to those found in lower redshift
galaxies for similar stellar masses ($\sim10^{10}\ M_\odot$). The REBELS
galaxies appear to follow the standard scaling relations of molecular gas to
stellar mass ratio ($\mu_{\rm mol}$) and gas depletion timescale ($t_{\rm
dep}$) with distance to the star-forming main-sequence expected from
extrapolations of $z\sim1-4$ observations. We find median values at $z\sim7$ of
$\mu_{\rm mol}=2.6_{-1.4}^{4.1}$ and $t_{\rm dep}=0.5_{-0.14}^{+0.26}$ Gyr,
indicating that the baryonic content of these galaxies is gas-phase dominated
and little evolution from $z\sim7$ to 4. Our measurements of the cosmic density
of molecular gas, log$(\rho_{\rm mol}/(M_\odot {\rm
Mpc}^{-3}))=6.34^{+0.34}_{-0.31}$, indicate a steady increase by an order of
magnitude from $z\sim7$ to 4.
