Mark blends them so thoroughly that he names only the better-known prophet when he attributes them: Isaiah. This is helpful in focusing the reader’s attention on the larger context of this section of Isaiah, as noted in the preceding post on Mark 1:1.

But what about Malachi? Does Mark think at all of Malachi’s context? Malachi expects consuming fire when YHWH comes (Mal 3:2; 4:1), an expectation also held by John the Baptist in Matt 3:11//Luke 3:16. But Malachi returns to the preparer in Mal 4:5-6: this is the prophet Elijah, who will turn or restore people’s hearts, preparing them lest YHWH strike the land when he comes. (Jesus uses the Greek version’s term for “restore” for John’s mission as Elijah in Mark 9:12; it applies to Jesus’s healings in Mark 3:5 and 8:25.)

This verse prepares us to recognize John the Baptist as the promised preparer for YHWH. Sure enough, John is recognizable as Elijah in Mark’s introduction. He does not call down fire on his challengers or on a sacrifice on a mountain. What he does do is come at the Jordan (Mark 1:5), in the wilderness (Mark 1:4), and, most distinctively, wearing a leather belt around his waist (Mark 1:6). Elijah had ascended just past the Jordan (2 Kgs 2:6, 13), had spent time in the wilderness (1 Kgs 19:4), and, most importantly, is depicted specifically as wearing a leather belt around his waist (2 Kgs 1:8). However common or uncommon such belts may have been, the only passage in the Old Testament mentioning a leather belt is 2 Kgs 1:8, and the only passages in the New Testament mentioning it are those introducing John (Matt 3:4; Mark 1:6). Both use exactly the same two terms; this is the New Testament’s only use of the term translated “leather.”

Why is it so significant that John fills a role like Elijah? If John fulfills Malachi 3:1, then John prepares the way for YHWH. But Mark identifies John as preparing the way for the Spirit-baptizer (Mark 1:8), for Jesus. In the Old Testament, only YHWH may pour out YHWH’s own Spirit. Mark thus recognizes that Jesus is YHWH himself, the one who baptizes in the Spirit (Mark 1:8). Ergo: Jesus is Lord.