A.T. Robertson Commentary Luke 3:5

"Every valley shall be filled, And every mountain and hill shall be brought low; And the crooked shall become straight, And the rough ways smooth;" — Luke 3:5 (ASV)

Valley (φαραγξ). Here only in the N.T., though in the LXX and ancient Greek. It is a ravine or valley hedged in by precipices.

Shall be filled (πληρωθησετα). Future passive indicative of πληροω. In 1845 when the Sultan visited Brusa the inhabitants were called out to clear the roads of rocks and to fill up the hollows. Oriental monarchs often did this very thing. A royal courier would go ahead to issue the call. So the Messiah sends his herald (John) before him to prepare the way for him. Isaiah described the preparation for the Lord's triumphal march and John used it with great force.

Hill (βουνος). Called a Cyrenaic word by Herodotus, but later Greek writers use it as does the LXX.

Brought low (ταπεινωθησετα). Future passive indicative of ταπεινοω. Literal meaning here of a verb common in the metaphorical sense.

Crooked (σκολια). Common word, curved, opposite of ορθος or ευθυς, straight.