  We propose a novel method to measure the $E_G$ statistic from clustering
alone. The $E_G$ statistic provides an elegant way of testing the consistency
of General Relativity by comparing the geometry of the Universe, probed through
gravitational lensing, with the motion of galaxies in that geometry. Current
$E_G$ estimators combine galaxy clustering with gravitational lensing, measured
either from cosmic shear or from CMB lensing. In this paper, we construct a
novel estimator for $E_G$, using only clustering information obtained from two
tracers of the large-scale structure: intensity mapping and galaxy clustering.
In this estimator, both the velocity of galaxies and gravitational lensing are
measured through their impact on clustering. We show that with this estimator,
we can suppress the contaminations that affect other $E_G$ estimators and
consequently test the validity of General Relativity robustly. We forecast that
with the coming generation of surveys like HIRAX and Euclid, we will measure
$E_G$ with a precision of up to 7% (3.9% for the more futuristic SKA2).
