“The righteousness of the righteous is that righteousness which is from Christ, for He has been "made unto us . . . righteousness" (1 Co 1:30). The same is for those even before the coming of Christ, which God mentioned to Adam and Eve concerning the coming of Christ; “And I will put enmity Between you and the woman, And between your seed and her Seed; He shall bruise your head, And you shall bruise His heel.” (Gen 3:15 NKJ).
“Now therefore why tempt ye God, to put a yoke upon the neck of the disciples, which neither our fathers nor we were able to bear? But we believe that through the grace of the Lord Jesus Christ we shall be saved, even as they (“they”; “our fathers”; OT saints – Acts 15:10, 11).
When we accept Christ we take on His righteousness and therefore, we have righteousness but it is inherent, by imputation; our righteousness is not our own but from Christ because it is His in us.
"For I say unto you, That except your righteousness shall exceed the righteousness of the scribes and Pharisees, ye shall in no case enter into the kingdom of heaven" (Mat 5:20):
"He mentions the Scribes, because they were the more learned part of the people, who were employed in writing out, and expounding the Law; and the Pharisees, because they were the strictest sect among the Jews for outward religion and righteousness and yet, their righteousness was very defective; it lay only in an external observance of the law which did not arise from a purified heart or the principles of grace.
“Nor was it performed sincerely and with a view to the glory of God; but for their own applause and in order to obtain eternal life. Besides, they neglected the weightier matters of the law and contented themselves with the lesser ones and as they were deficient in their practice, so they were very lax in their doctrines, as appears from the foregoing verse.
“A "pharisaical" righteousness will never bring a person salvation, nor will any righteousness of man's, be it what it will, because the best is imperfect. It must be a righteousness exceeding that of the Scribes and Pharisees and such is the righteousness of the saints, which is their inherent righteousness or the sanctification of the Spirit.
“But, above all, the righteousness of Christ, which is imputed to them and received by faith, is infinitely more excellent in its author, perfection, purity, and use; and which is their only right and title to eternal glory and without which no man will be admitted into that glorious state." -JG
"And they were both righteous before God, walking in all the commandments and ordinances of the Lord blameless" (Luke 1:6): “were both righteous before God”; Not as the Pharisees, only righteous before men, but in the sight of God, who sees the heart, and whose judgment is according to truth and therefore were not justified by the deeds of the law; for by them no man can be justified in the sight of God; but were made righteous through the righteousness of Christ, by which the saints were made righteous before the coming of Christ, as those after it (Acts 15:10, 11).
“God beheld them in His Son, as clothed with that righteousness He engaged to bring in and as cleansed from all sin in that blood of His which was to be shed. They appeared to Him, and in the eye of His justice and according to His law, righteous persons. This character may also regard the internal holiness of their hearts and the truth and sincerity of grace in them which God, who tries the hearts and reins of the children of men, knew, took notice of and bore testimony to.
“As likewise their holy, upright walk and conversation before men, and which was observed by God, and acceptable to Him, though imperfect, as arising from a principle of grace, being performed in the faith and fear of Him and with a view to His glory and for the sake and righteousness of His Son.” -JG