Whom is the quotation, "behold, I send my messenger before your face, who will prepare your way," taken from?

According to most commentators, the reproduction of Malachi 3:1 in Mark 1:2b is influenced indirectly by the text of Exodus 23:20. Indeed, Gundry wonders if the similarity with Exodus is perhaps greater than with Malachi.¹ While in Malachi the Lord speaks about a person who is being sent before me, Exodus speaks of an angel before you, which Mark 1:2 does also. However, we should continue to regard this verse at the beginning of Mark as a reference to Malachi. That prophet (Malachi 3:1) speaks, just like Mark, about the preparation or construction of a way, whereas Exodus speaks about being guarded on the way. Precisely because both Malachi and Mark speak of a way that God builds between himself and his people, we can speak about a way before God’s face (Malachi), as well as a way before the face of the people (Mark). Although considered from two different aspects, in substance the topic is the same. God prepares a way between himself and his people.²