Caution with Bein Adam l'Chaveiro

It states (11:7) לְשֹׁנוֹ כֶּלֶב יֶחֱרַץ לֹא יִשְׂרָאֵל בְּנֵי וּלְכֹל, which means that on the night of yetzias Mitzrayim, no dogs barked before a Yid. Hinted in these words is another lesson. לְשֹׁנוֹ ...יֶחֱר ַץ, alludes to sharp words. The Ruzhiner zt'l (Irin Kadishin) explains that the pasuk hints at the prohibition of speaking sharply and unkindly to one's fellow man.