Chazal
Chazalתַּנְיָא, בִּשְׁפִיכוּת דָּמִים כְּתִיב גָּדוֹל עֲוֺנִי מִנְּשֹׂא, וּבְלָשׁוֹן הָרָע כְּתִיב לָשׁוֹן מְדַבֶּרֶת גְּדֹלוֹת, לְלַמֶּדְךָ שֶׁכָּל הַמְסַפֵּר לָשׁוֹן הָרָע מַגְדִּיל עֲוֺנוֹ כְּנֶגֶד עֲוֺן שְׁפִיכוּת דָּמִים.
It was taught: Concerning bloodshed it is written “My iniquity is too great to bear,” and concerning evil speech it is written “a tongue speaking great things,” to teach you that whoever speaks lashon hara magnifies his iniquity to the measure of the iniquity of bloodshed.