הלכה אויף שמות 2:14

And we find it explicitly stated that it was this sin which caused the Jews to be worked [by the Egyptians] with back-breaking labor (viz. Shemoth 2:14 and Rashi there). And (Devarim Rabbah 6:14): "The Holy One Blessed be He said: 'In this world, because there was lashon hara among you, I removed My Shechinah from you, but in the next world, etc.'" And (Devarim 33:5): "And He became a King in Yeshurun when the heads of the people were gathered together as one, the tribes of Israel," which Rashi interprets (as per Sifrei): "When is He a King in Israel? Specifically, when the tribes of Israel are united and not divided into factions" — which (factions) are well known to be the result of lashon hara.