But if a man be just, and do that which is lawful and right,
But if a man be just. Here begins the illustration of God's impartiality in a series of supposed cases: Firstly, from Ezekiel 18:5-9, the just man; the excellences are selected in reference to the prevailing sins of the age, from which such a one stood aloof; hence, arises the omission of some features of righteousness which under different circumstances would have been desirable to be enumerated. Each age has its own besetting temptations, and the just man will be distinguished by his guarding against the special defilements, inward and outward, of his age.
Just ... lawful ... right - the duties of the second table of the law, which flow from the fear of God. Piety is the root of all charity: to render to each his own, as well to our neighbour as also to our God.