The answer is: Isaiah

Isa 40:3

In the Gospel of Mark, the wilderness voice calling for preparation naturally leads us straight to Isaiah, a prophet with a powerful message of comfort and hope. Mark first presents Isaiah's words in chapter 1:3, setting the stage for the dramatic entry of Jesus into the world. Isn’t it interesting that Isaiah, who lived centuries before Christ, had such a finger on the pulse of what was to come?

Amid Israel's turmoil, Isaiah promised that someone powerful would arrive to level the playing field, literally paving the way for God's people. This imagery of the "voice in the wilderness" not only highlights the importance of being ready for spiritual renewal but also marks the arrival of a transformative figure in Jesus, who would redefine society’s norms.

Now, here's a fun fact for you: Isaiah is frequently referenced throughout the New Testament—over 200 times! This illustrates just how central his technique of speaking to societal needs was throughout the Hebrew scriptures and onto the New Testament. His voice resonates right until today, echoing messages about love, justice, and redemption.

Moreover, many see the specific emphasis on "wilderness" landscapes in this context as an evocative return to ancient places where foundational moments in spiritual journeys took place—echoing experiences from Moses to John the Baptist's wilderness calls. Such connections enrich our understanding of the biblical narrative as we recognize the continuity of God's promises and human experiences spanning allegorical landscapes through generations.