Barking dogs seldom bite

सम्पूर्णकुम्भो न करोति शब्दम्
अर्धो घटो घोषमुपैति नूनम् ।
विद्वान् कुलीनो न करोति गर्वम्
गुणैर्विहीनाः बहु जल्पयन्ति ॥

A pot fully filled (with water) never makes any noise. However a half filled pot definitely makes a lot of noise. A learned person is never vain, as opposed to people devoid of qualities who keep babbling.

Barking dogs seldom bite.
Great talkers are little doers.
An empty vessel makes the most noise.