The voice of one who calls out, “Prepare the way of Yahweh in the wilderness! Make a level highway in the desert for our God. Every valley shall be exalted, and every mountain and hill shall be made low. The uneven shall be made level, and the rough places a plain. Yahweh’s glory shall be revealed, and all flesh shall see it together; for the mouth of Yahweh has spoken it.”
The voice of one crying in the wilderness, Prepare ye the way of the Lord, make straight the paths of our God. Every valley shall be filled, and every mountain and hill shall be brought low: and all the crooked ways shall become straight, and the rough places plains. And the glory of the Lord shall appear, and all flesh shall see the salvation of God: for the Lord has spoken it.
Where this passage surfaces again, sorted by the strength of the link. Each kind of reuse — formal quotation, deliberate allusion, faint echo, figural pattern — carries its own mark. Follow any reference to read it in place.
Quotation1
A formal citation — high verbal volume, often introduced by a saying-formula.
Luke gives the fullest NT citation of Isaiah 40:3-5, uniquely extending the quotation through v.5 to "all flesh shall see the salvation of God," following the LXX (which reads "the salvation of God" where MT has "the glory of the LORD"). The explicit citation formula ("as it is written in the book of the words of Isaiah") and verbatim LXX wording give maximal Volume; the extension serves Luke's universal-salvation theme.
High confidence◇ Figural1
A typological pattern re-read in a later text — no verbal quotation, high figural coherence.
Beyond the quoted v.3, the whole Isaianic New Exodus / wilderness-highway scene shapes the pericope: comfort after exile, the revealing glory of the Lord, all flesh seeing salvation. The wilderness setting of John's preaching enacts the prophetic return-from-exile pattern.
Medium confidence