Jesus continues on to say “Blessed are those who mourn, for they will be comforted. Blessed are the meek, for they will inherit the earth. Blessed are those who hunger and thirst for righteousness, for they will be satisfied” (5:4-6). His use of “righteousness” helps to mark a transition. “Righteousness” is best understood as “covenant faithfulness.” This, of course, is what the Creator God has always expected from His people---faithfulness to their covenant responsibilities to represent Him and to be a light to the nations for the purpose of His glory. Understandably then, almost immediately after finishing His “outline,” Jesus reminds those that want to participate in the kingdom of heaven (come to earth) that they are to be “the light of the world” (5:14a).
Though this should not be done too often (as it is paramount to let the Gospel narratives speak for themselves, as they are informed by the history of Israel and the implications of Jesus’ Resurrection), when considering the idea that “righteousness” is to be equated with “covenant faithfulness,” it is useful to look to one of Paul’s letters. Naturally, it is not unreasonable to consider the possibility that Paul’s theological outworking of the meaning behind the crucifixion and Resurrection of Jesus had a role in shaping the theology that stands behind Matthew and the other Gospels, and therefore also played a part in giving shape to the narrative form that would be taken by the Gospels. Additionally, looking to Paul, while also looking back into the history of Israel, one can get a sense of the thinking in the time of Jesus concerning this important subject.
In his second letter to the Corinthian church, Paul insists that at least one of the purposes of the covenant God’s redeeming activity is that “in Him,” that being Jesus (“in Him” as a shorthand way of saying that it is through calling Jesus Lord, in a pledged oath of loyalty, that all are enabled to enter into the grouping of the Creator God’s covenant people), “we would become the righteousness of God” (5:21b).
In short then, Paul says that the Creator God desires that His people be the ones to carry out that which represents His covenant faithfulness, as “ambassadors,” with “God making His plea through us” (5:20), having given over to His covenant bearers (obviously, through the working of the Holy Spirit), His “ministry of reconciliation” (5:18)---the covenant God’s reconciling His people and His divine image-bearers to Himself as part of His redemptive plan for His world that Paul refers to as “new creation” (5:17). This happens, of course, because “the love of Christ,” which was demonstrated by His willing and self-sacrificial death, and by which He gave proof to the conviction behind His kingdom plans and principles, and which believers should seek to imitate in principle if not in form, “controls us” (5:14a).
Returning to Matthew then, and considering Jesus’ introduction of “righteousness” or “covenant faithfulness” into the sermon, one can see that Jesus proceeds to give at least a partial summary of the form that will be taken by that execution of righteousness (covenant faithfulness). Jesus says “Blessed are the merciful… Blessed are the pure in heart… Blessed are the peacemakers” (5:7a,8a,9a). Those that demonstrate these characteristics will “be shown mercy… will see God… will be called the children of God” (5:7b,8b,9b).
Amazingly enough, however, Jesus indicates that those that live in such ways, rather than being universally praised and lauded for their fine demonstration of their alignment and agreement with the principles of the kingdom of heaven, will be “persecuted for righteousness” (5:10a)---persecuted for the way that they demonstrate their faithfulness to the covenant and the way that they insist upon people entering into the covenant. In fact, those that insist upon this way of bringing in, establishing, and expanding the Creator God’s kingdom will have an altogether unexpected experience, as they will be insulted and persecuted, whilst people speak evil of them on account of their loyalty to Jesus.