Romans 5:19

‘For as through the one man's disobedience the many were constituted sinners, even so through the obedience of the one shall the many be constituted righteous.'

It will be noted all through that Paul never states quite how the one man's trespass/disobedience constituted many as sinners, only that it did so, as something evident from the facts of history. The most reasonable explanation is that it did so by passing on the taint of sin so that all men sinned as Romans 5:12 declares. Here again then we are reminded that the one man's disobedience resulted in many being constituted sinners. In contrast through the obedience of the One many will be ‘constituted righteous'. That this refers to our being ‘reckoned as righteous' has been the emphasis of Romans 3:24 to Romans 5:11. Thus because Jesus Christ was fully obedient in all things (Hebrews 10:5), and especially in relation to His death (He was ‘obedient unto death' - Philippians 2:8), He is able to put that obedience to our account. Through it we can be ‘constituted righteous', that is, ‘accounted as righteous'. The idea is taken from Isaiah 53:11, ‘by His humiliation will my righteous Servant make many to be accounted righteous'. (The Hebrew word yatha‘, normally translated ‘knowledge', also at Ugarit signifies ‘humiliation').