Preliminary definition: The Righteousness of God is that He keeps his threats (Law, justice) and His promises (Gospel, grace, Neh. 9.8) (Rom. 3:26) and restores original righteousness through faith in Christ (Phil. 3.9).
Ex. 34:6
Neh. 9.8, 33
Rom. 3.26
Phil. 3.9
God’s righteousness = salvation
Ps. 71:15, 98:2; Isa. 46:13, 51:5–6, 59:17
Gibbs, Matthew, v. 1, p. 180
Aug. De spirit. et lit., c. 32: Charitas quippe Dei dicta est diffundi in cordibus nostris, non qua nos ipse diligit, sed qua nos facit dilectores suos : sicut iustitia Dei, qua iusti eius munere efficimur; et Domini salus, qua nos saluos facit; et fides Iesu Christi, qua nos fideles facit. Haec est iustitia Dei, quam non solum docet per legis praeceptum, uerum etiam dat per Spiritus donum.
Augustine (On Psalm 109): "God is faithful, for He makes Himself our debtor, not by receiving anything from us but by promising us such great things."
Gerhard, On Election, 94.
Gerhard On 2 Timothy 4:8: “This righteousness of God, moreover, is not understood as the righteousness which judges according to the merits of works, but as the righteousness according to which God is faithful in his promises and which gives the wages not of merit but of His gracious promise.”
Gerhard (Good Works § 118): We respond in general. Eternal life is the χάρισμα (“free gift”) of God (Rom. 6:23), but it is called a “crown of righteousness” for three reasons: (1) because God’s righteousness in Scripture sometimes denotes the same thing as His mercy. Luther (Enarr. evang. 1. adv.)[1] writes: “Note this carefully: wherever you find in the Scriptures these words: ’the righteousness of God,’ do not understand this to mean the essential, interior righteousness of God. Rather, you should know that according to Scripture’s way of speaking this means God’s grace and mercy poured out on us through Christ through which we are reckoned righteous and upright before God. That is why it is called ’the righteousness of God,’ because it is not we but God who works this in us through grace,” etc. That this observation of Luther is most true is clear from several passages of Scripture in which “righteousness” can mean nothing else but God’s goodness and mercy. Ps. 51:14: “Free me from bloodguilt and my tongue will extol Your righteousness.” Ps. 143:1: “Answer me in Your righteousness, and do not enter into judgment with Your servant.” Dan. 9:16: “According to all Your righteousnesses turn away Your wrath.” For this reason the Latin translator sometimes even substitutes “mercy” for “righteousness.” Ps. 103:6: “The Lord works mercies,” though in Hebrew it reads, “He works righteousnesses.” So, then, eternal life is the crown of righteousness, that is, that by which “God crowns the godly with grace and mercy,” as it is explained in Ps. 103:4. Here belongs the observation that God is preached in the Scriptures to be “righteous” whenever He deals with us purely and only out of His mercy and apart from the intervention of our works. Rom. 3:25: “God set forth Christ as the propitiation through faith in His blood, to show His righteousness through the forgiveness of past sins.” (But now, the forgiveness of sins is the work of God’s free mercy.) 1 John 1:9: “If we confess our sins, God is faithful and righteous to forgive our sins and cleanse us from all iniquity.”