Romans 6:10

ὃ γὰρ�, ‘a kind of cognate accus. after the second ἀπέθανεν,’ S.H. His death that He died was a death once for all to sin.

τῇ ἁμαρτίᾳ. Cf. Romans 6:21, the sin that reigned by death: for the dative cf. Romans 6:2.

ὃ δὲ ζῇ, ‘the life that He lives is a life to GOD.’ It is clear that ‘the Death’ is not limited to the Death on the Cross. The whole life of Jesus was a death to sin, culminating in the final act of the Cross. So ‘the life’ here is not limited to the post-resurrection life: it is the life which He lived on earth, and still lives. Cf. the very remarkable phrase, 2 Corinthians 4:10, τὴν νέκρωσιν τοῦ Ἰησοῦ followed by ἡ ζωὴ τοῦ Ἰησοῦ. This meaning is well indicated by the strong ‘perfectivised’ ἀπέθανεν; cf. Moulton, p. 112.