Jude is mainly referring to the writings of Moses that they have been taught. Alternate translation: "you know the writings of Moses." (See: [[rc://en/ta/man/translate/figs-explicit]])
## the Lord once saved a people out of the land of Egypt ##
"the Lord rescued the Israelites long ago from Egypt"
## but that afterward ##
"at a later time" or "after something has happened"
## ...their own principality ##
Angels who did not keep to their positions or responsibilities entrusted to them.
## left they proper dwelling place ##
"they abandoned their own assigned places"
## God has kept them in everlasting chains in darkness ##