  We report a precise measurement of the hyperfine interval in the ${2P}_{1/2}$
state of $^{7}$Li. The transition from the ground state ($D_1$ line) is
accessed using a diode laser and the technique of saturated-absorption
spectroscopy in hot Li vapor. The interval is measured by locking an
acousto-optic modulator to the frequency difference between the two hyperfine
peaks. The measured interval of 92.040(6)~MHz is consistent with an earlier
measurement reported by us using an atomic-beam spectrometer [Das and
Natarajan, J.\ Phys.\ B {\bf 41}, 035001 (2008)]. The interval yields the
magnetic dipole constant in the $P_{1/2}$ state as $A=46.047(3)$, which is
discrepant from theoretical calculations by $>80$~kHz.
