And he shall go before him in the spirit and power of Elias, to turn the hearts of the fathers to the children, and the disobedient to the wisdom of the just; to make ready a people prepared for the Lord. (Luke 1:17 AV)
John was a forerunner, going before the Lord in the power of the Spirit of the Lord to create a people who would be prepared for the coming of the Lord.
The prior sentence said that John would "turn many of the sons of Israel to the Lord their God". This sentence uses several of the same words and grammatical structures and begins with "and". The spirit of Elijah was none other than the Spirit of the Lord, but Luke deliberately identifies Him in respect to Elijah rather than the Lord. The preparation of the people has two parts: The fathers are going to have hearts turned to the children; The disobedient are going to buy into the mindset of the just.
People are not "prepared" for the coming of the Lord unless they have a "children" focus and have a "justification" mindset. This is an interesting contrast to our focus on "asking Jesus to come into our hearts". Luke says we will be ready for the coming of the Lord when we are "children-focused" and we say we will be ready for the coming of the Lord when we have a "me-focus". The difference in the Gospel in Luke and the gospel of American "Christianity" is that Luke's Gospel saw the promise as a means to a different behavioral end produced by a different heart and mind and we see the promise as a means to a different destination produced by a different status (being "forgiven").
The statement "...to turn the hearts of the fathers upon the children..." is a partial, direct quote of Malachi 4:6 [the last verse of the Old Testament]. The other phrase ("the comprehension of the righteous") is not found in Malachi. The last phrase, "a people prepared" is a reference to Malachi 3:1 where the forerunner precedes the coming Lord Who will come to His temple. Most likely, in this text, Gabriel is identifying the major values-problem (fathers who are misguided in their values) and the major belief-problem (unpersuaded people who have no grasp of the understanding of the just, who are focused upon grace in two directions: first, in the direction of themselves as totally corrupt [in my flesh dwells no good thing]; and second, in the direction of Yahweh as completely dispensing with "demand" upon the corrupt so that they might have hope through promise without law.) In verse 16, Luke said that John would "turn" many of the sons of Israel "upon" Yahweh their Elohim. He uses the same word "turn" when he says the hearts of the fathers will be turned "upon" the children [this probably explains the joy of Zacharias as coming from the characterization of John--a father whose heart has been turned to his child cannot but rejoice when the child makes a significant impact for God]. This introduces an interesting explanation for what it means to "turn to the Lord our God". It makes the "children" the equivalent to "the Lord our God" and our attitude toward the children the equivalent to our attitude toward the Lord our God. This is precisely what Jesus said in Luke 9:48: "he that receives this child...receives Me...". That reinforces the fact that God has always seen the promise of the Gospel as a means to altering the way we do things -- i.e., God is focused upon our works and sees the promise as a way to determine what they will be. How did we get so far off track as to think that our works are completely off the radar screen? Just because we are not saved by our works does not mean that our works are of no consequence. The only reason that the focus of the Gospel is upon "faith apart from works" is that this is the root that will yield the proper fruit -- a healthy distrust of ourselves [those who walk in pride, He is able to abase] coupled to a healthy trust in the God of Promise [the fearful and unbelieving shall be cast into the Lake of Fire] -- John's "repentance" thesis! In Luke's record of John's impact, we see certain "disciples of John" who began to follow Jesus with a relatively high degree of commitment [they dropped their vocations and pursuits to follow Him] and maintained an independence from the commitment to the children [He had to scold them rather vehemently for their rejection of the children]! In what sense, then, was he effective in turning the sons of Israel to the Lord? In the sense of the forerunner who would only be able to baptize with water but who would introduce One Who would baptize with the Holy Spirit and fire. In other words, the "turning" to the children is neither immediately nor consummately accomplished by the forerunner. It is like a seed that, once planted, eventually produces what it was designed to produce. This is the nature of Promise: the initiation is the barest of seeds [like the proverbial mustard seed]; the fruition is the magnificent final result [like the greatest of the plants of the garden]. It is helpful, however, for the recipients of the promise to understand from the outset what the objective of God is and will be in its ultimate form -- hearts turned to the children. The term translated "prepared" is a term that means that everything that needed to be done to make it possible for the "prepared thing" to function as it was intended has been done.