Romans 3:25

whom God set forth to be. propitiation, through faith, in his blood, to show his righteousness because of the passing over of the sins done aforetime, in the forbearance of God;

'Set forth' -publicly, openly.

'Propitiation' -satisfaction, appeasement, having. placating or expiating force. To propitiate is to appease, to render favorable.

In the Greek translation of the Hebrew Scriptures (LXX), this is the word used to describe the 'mercy seat', where atonement was made in the O.T. In contrast, the true "means" of appeasing the penalty that sin demands, wasn't veiled or hidden, but publicly shown to all, i.e. Christ died in full public view.

'through faith' -such appeasement for sin does have conditions.

'in his blood' -again, not just faith 'in' anything.

'to show his righteousness because of the passing over of the sins done aforetime'

'to show' -to demonstrate. God cannot just let sin slip by. If sin in the past was left unpunished was it because God was ignoring it? Did he think it wasn't very important? This phrase teaches the truth, that if patience was shown to sinful men and sins in the past, it was IN VIEW OF THE COMING SACRIFICE OF CHRIST. God's justifying us, MUST OF ITSELF BE JUST. God cannot deliver us by an unrighteous method. (Acts 17:30) Here we encounter another passage that teaches that the benefits of the blood of Christ flow both ways (Hebrews 9:15)

'That is, to demonstrate that God was not unrighteous when He passed over (left unpunished) sins committed in earlier days, in the period of His forbearance.'