νόμος δὲ παρεισῆλθεν ἵνα πλεονάσῃ τὸ παράπτωμα (5:20–21)

Says παρεισῆλθεν (pareisēlthen): Abbott-Smith "to come in beside or by the way" (Rom 5:20; "steal in," Gal 2:4). The law came in alongside, between Adam and Christ. Where sin ἐπλεόνασεν (epleonasen, "increased"), grace ὑπερεπερίσσευσεν (hypereperisseusen, "increased all the more"; Abbott-Smith "to abound more exceedingly").

Uncertain ἵνα πλεονάσῃ (hina pleonasē). This note leans to purpose: the law was given "so that the trespass would increase" (BSB), sin becoming open transgression of a command (4:15; 7:7–13). Grounds: ἵνα with the subjunctive is "final, denoting purpose" (Abbott-Smith); the ἵνα of 5:21 is purpose; Gal 3:19 says the law was "added because of transgressions." The alternative is result, "with the result that the trespass increased." Grounds: Abbott-Smith lists an "ecbatic, denoting the result" ἵνα in later Greek (Rom 11:11), and 7:13 makes sin, not God, the agent of the increase.

Says 5:21 sets two reigns side by side: sin ἐβασίλευσεν ἐν τῷ θανάτῳ, and grace is to reign διὰ δικαιοσύνης εἰς ζωὴν αἰώνιον through Jesus Christ. 6:1 takes up the objection that follows.