Paul is in the midst of his discussion that really began in the first chapter of Romans when he talks about the "faith to faith." (Romans 1:15-17) Those verses almost "set the tone" for many of the in-depth, doctrinal points that Paul will investigate. But, as Paul continues his journey to the point we are currently at, he goes by way of discussion on Gentile behaviour before the gospel came unto them. He discusses in the second chapter about Gentiles that kept the law having never heard or received the law. They became a law unto themselves because they were  showing forth a changed heart that had God's precepts stamped upon it, even though they were never in contact with the letter of it. (Romans 2:14-15) Then, Paul opens the third chapter with some rousing questions. The first question is the advantage of a Jew over a Gentile? The chief advantage is that they had the oracles of God. They knew what God commanded explicitly, whereas a born-again Gentile knew only the law of God implicitly.

Then, Paul goes on from that discussion and series of questions to deny any case for national partiality in the eternal throneroom of God. Paul lays out a "cadaver" of man's filth that shows forth all (without exception) are fully under sin by nature. (Romans 3:9-18) No Jew could claim natural superiority to the Gentile as both were born in complete and total depravity. Then, Paul leaves this woeful picture by summing up that we have all come short of the glory of God (verse 23) to discussing the work of Jesus Christ for His people. God showed faith in the blood of His Son to be a propitiation for the sins of the elect family of God (Jew and Gentile alike). Due to this work of Jesus Christ, we have complete and free justification by His grace and redemption. (verses 24-26) Paul makes it explicitly clear that whatever group one wants to make, there is one group that truly matters: the group that Christ died for. Whether one is a Jew or Gentile matters little, but whether one is Christ's or not matters much.

Now, after discussing what Christ has done, Paul states that justification comes by faith without the deeds of the law. (verse 28) Now, this justification must be different than the justification in verse 24 as one is by faith and the other by grace. The first is the justification that we have in God's court by the grace and blood of Jesus Christ. The second is the justification that we have in our own court (mind) that comes by faith. This is the faith of Abraham that will be discussed in depth in chapter 4. This does not give us any right to glory in God's court (only blood and grace can be gloried in there), but it does give sweet assurance that we are His and blessed by Him. Without faith, that assurance is absent, and the faith testifies that God is one with us. So, now that we have gotten to the verses above, what do we make of the difference of wording between Jew and Gentile?

One school of thought (that I have no qualms with) is that Paul is merely avoiding repetitive language.  The "by faith" and "through faith" are one in the same but using different words to avoid repetition.  Another thought that can be brought forth is the difference of testimony to a Jew and Gentile. The word "by" is a preposition that denotes being "out from, or place from whence something proceeds." When the born-again Jews were first given the gospel of a risen Christ, they had places to start from and come from. Their chief claim over a Gentile was the oracles of God. They could see the many infallible proofs that this Jesus is the very Christ. Prophecy after prophecy manifestly was fulfilled. They had an origin (in the letter) that their faith could bring out and come out from. But, to a born-again Gentile that first hears the gospel, he has no prior
acquaintance with the prophecies and precepts of thelaw and the prophets. So, how does his faith justify him in his mind?

The preposition "through" is the primary preposition that "denotes the channeling of an act." Since a born-again Gentile had no place of origin (law of Moses) to come from, the gospel had to acquaint Him with Jesus AND the proofs that would convince him of what a Jew would be convinced of by just hearing about Jesus (provided of course that the Lord blessed the opening of the eyes and ears in the preaching of the gospel). For instance, you could tell a Gentile," This Jesus raised the dead, cleansed the leper, made  the blind see, the deaf hear, and the lame walk."

But, since he has not read the book of Isaiah, that may not tell him that Jesus is Emmanuel or God with us. One must go through the channel of the the prophecy and works to show forth these things. His faith (while the same as the Jew) had to come to knowledge that the Jews already had from youths before he had the knowledge to say, "I feel to be one of His."

Indeed, justification by faith comes to give us peace with God. (Romans 5:1) God is at peace with us, His people, but for us to have peace in our own minds that He smiles upon us, faith must testify to these things. The more we know about the story of our Saviour, the more peace and rest we will find. As He told those in Matthew 11:28 to come and take His yoke upon them. There is something between taking His yoke  and finding rest for our souls. In between, we read that we must learn of Christ, and I can say, with full assurance, that the more we learn of Him the more rest we will find. We may learn some things BY principles that we were already acquainted with, but we may also have to learn some things never known to us and come THROUGH some things to gain that understanding. But, thanks be unto God that whatever our circumstance, He is the God of both. While we may discuss from time to time what the difference is in "by faith" and "through faith," I am thankful most of all for the phrase, "Seeing it is one God," as that declares that the rest
all belongs to Him. Let us thank Him for justifying us freely by His grace and the blood of His Son, and press to the mark of Christ to find sweet rest for our souls.

In Hope,

Bro Philip