The answer is: Isaiah

Isa 40:3

In the Gospel of Mark, you’ll instantly notice that quotes from various prophets serve a vital role in establishing key themes and identity. Isaiah, that grand Old Testament prophet, is quoted from the very beginning in Mark 1:2-3 as he foretells prepare the way for the Lord. This powerful imagery of preparing a path is just the tip of the iceberg when it comes to understanding the significance of Mark's approach.

Isaiah's soaring language emphasizes a herald or a messenger, reflecting the prophetic tradition of calling God's people back to fidelity with their Creator. It assimilates beautifully with Mark's intention to introduce the coming of Jesus. Interestingly, this isn’t just a blunt quote; it's peppered with resonances. For the Israelites, waiting for the same kind of 'preparer' signified deeply held aspirations for salvation and liberation.

By opening with Isaiah, Mark bridges the gap between centuries of prophetic history and the arrival of Jesus, effectively claiming that Jesus is a continuation and fulfillment of those prophetic voices. Fun fact: The full meaning in the quote includes nuances from offerings before a king, which you can really see mirrored in the way John the Baptist acts in the wilderness. It's a perfect stage-setting for a story about a revolutionary figure! Isn’t it fascinating how the artistry of linking Old and New creates a thread of hope woven through Scripture?