The Isaian citation, used by Paul to describe his encounter with certain Jews in Rome, does not stand alone: it leads to a conclusion, a conclusion which is an imperative and an assurance. What is commanded is a knowledge of the plan of
God already in motion, a plan to offer salvation to Jews and Gentiles. As information for Jews of Rome, this final word of Paul is best understood as a motive for repentance; knowledge of the divine plan of God, which will succeed (28b), serves as an encouragement to Roman Jews to «turn and be healed by Me».
All Jewish religious teachers wanted sinners to repent; how one achieves this was disputed, as was Jesus’ choosing to associate with sinners in their houses and at their meals. Four times Luke describes Jesus as fraternizing with sinners, which violated Jewish pious practice. The first three times (chaps. 5, 7 and 15) Jesus underlines his motive for this conduct and its value; the fourth time (chap. 19), and rather late in the Gospel, Luke shows that indeed Jesus’ method proved true, i.e. the wisdom of his conduct was shown justified by repentant children of God.