whom God has set forth a mercy-seat, through faith in his blood, for [the] shewing forth of his righteousness, in respect of the passing by the sins that had taken place before, through the forbearance of God;
I do not think this word can be used for '[a] propitiatory [sacrifice]' or 'propitiation;' it certainly is not the habitual use in the LXX; and we have the two parts of the work of the great day of atonement, here and in ch. 4.25; 'set forth,' here, has a reflexive force; see Note e, Heb. 1.3.
'In respect of the passing by the sins.' I have hesitated as to using dia with the accusative in this sense here; but on the whole I do not doubt it gives the sense. God had passed by, not brought into judgment, the sins of Old Testament believers; and the accomplishment of the atonement showed His righteousness in this. Now the righteousness is itself shown, and to be relied on.