Where Does Our Righteousness Come From?

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Who are the Judaizers?

The Apostle Paul warns his readers about the Judaizers who oppose the gospel (Phil 3:2–3). Paul’s conflicts with the Judaizers can be seen in greater detail in Acts and Galatians (e.g., Acts 15:1–19; Gal. 2:15–21; 3:6–4:31), as well as in the rest of his letters. Paul rejected their teaching that Gentiles must first become Jews and obey all the OT laws in order to be saved. In contrast, Paul has given up his spiritual and ethnic privileges for the sake of knowing Christ (Phil. 3:4–11). His righteousness comes through Christ, not the law (Phil 3:12–16).

The justified /righteous person in the New Testament

“Justified” means “counted righteous” or “declared righteous” by God (acc. to ESV footnote).
If people obeyed all of God’s perfect moral standards, they could be justified by their own merits. But Paul says that this is impossible for anyone to do (see Romans 1–2). "Works of the law" means any human effort to be justified by God by obeying a moral law.
We also have believed in Christ Jesus, in order to be justified by faith in Christ implies that justification is the result of saving faith, and not by works of the law. No human effort or merit can be added to faith as a basis for justification (see Acts 13:39; Gal. 3:10–14; Heb. 10:1–14).
On justification, see also Paul's teachings @ Rom. 4:25; James 2:21.
^{This note is based on the article of the ESV Study Bible}