There are some things hard to understand in Paul's writings and other texts. The Good News of Messiah straightens them all out. Here are the highlights:
No. 1: "To justify" (δικαιοῦν) someone in Ancient Greek normally meant "to administer justice" to him. A judge would administer justice to a guilty defendant by either pardon, or punishment. He would "justify" the defendant, i.e. apply justice to him. God likewise applies justice to the faithful through his Son. The notes provide examples from the Jewish historian Josephus and the Roman historian Cassius Dio.
No. 2: The words "faith" and "believe" in the usual English versions are mistranslations. The noun (πίστις) means "faithfulness" and the verb (πιστεύειν) means "to hold faithful" to someone or to hold something faithful. The noun and verb are derived from the adjective "faithful" (πιστός), which is synonymous with the verb (πείθειν) "to obey." Out of more than 500 instances of these words most are conformed to these standards.
No. 3: Often when Paul speaks of "faithfulness" (πίστις) he means Mĕssiah's faithfulness. See Rom. 3:22, 26; Gal. 2:16, 20; 3:22, 26; Phil. 3:9. These are the famous passages of the πίστεως Χριστοῦ debate explained by Wright and Hays. The author of the Good News of Messiah came to the same conclusions years before hearing of these scholars.
No. 4: Paul sometimes rejected works (cf. Rom. 3:20; Eph. 2:9; Titus 3:5) and other times he taught good works (cf. Rom. 2:7, 13; Eph. 2:10; Titus 3:8). If a reader was uninformed about the Jewish context, then he could distort Paul's meaning to be a rejection of Gŏd's commandments. The notes explain that Paul was rejecting the Rabbinical doctrine of merits: the use of merits to pay off the debt of demerits.
No. 5: Sometimes Paul used the word "law" in ways unfamiliar to the modern mind, but well known in Koine Greek and to careful scholars, such as a custom, or habit, or a legal norm, or a social status quo, besides the well recognized use for the Law of the Almighty. Gregg sorts all these senses out in the Good News of Messiah with careful attention to the internal and external context