  We report the first $5\sigma$ detection of HI 21 cm emission from a
star-forming galaxy at redshift $z\sim1.3$ (nearly 9 billion years ago) using
upgraded Giant Metrewave Radio Telescope (uGMRT). This is the highest redshift
HI detection in emission from an individual galaxy to date. The emission is
strongly boosted by the gravitational lens, an early type elliptical galaxy, at
redshift $z \sim 0.13$. The measured HI mass of the galaxy is $\rm M_{HI} =
(0.90 \pm 0.14 \pm 0.05) \times 10^{10}M_{\odot}$, which is almost twice the
inferred stellar mass of the galaxy, indicating an extended structure of the HI
gas inside the galaxy. By fitting two-dimensional Gaussian to the HI signal at
the peak of the spectral line, we find the source to be marginally resolved
with the position angle consistent with the emission being tangential to the
critical curve of the lens mass distribution. This indicates that the solid
angle of the approaching HI line flux comes very close to the inner lens
caustic and results in very high magnification. These results, for the first
time, demonstrate the feasibility of observing high redshift HI in a lensed
system with a modest amount of telescope time and open up exciting new
possibilities for probing the cosmic evolution of neutral gas with existing and
upcoming low-frequency radio telescopes in the near future.
