This is a pivotal point in the book transitioning from explanations of cause to descriptions of effects. This is a pattern seen in a number of the epistles that were written. It is very important to see the instructions in the last part of these writings in the context of the realities described in the part preceding them or they can easily become very discouraging.
“Therefore” is an alert word that reminds us to look back and find the reason for what is about to be said. It is parallel to saying “for this cause” and other such similar words and phrases. If it is disconnected from its root then we are guaranteed to fail in understanding the text properly.
So, for my part, I am eager to preach the gospel to you also who are in Rome. (Romans 1:15)
I have great sorrow and unceasing grief in my heart. For I could wish that I myself were accursed, separated from Christ for the sake of my brethren, my kinsmen according to the flesh. (Romans 9:2-3)
Brethren, my heart's desire and my prayer to God for them is for their salvation. (Romans 10:1)
Therefore I urge you, brethren, by the mercies of God...
Paul was far more than a highly educated scholar and a very effective missionary and preacher. He was a man very much in touch with his heart and his emotions and he was not reluctant to allow others to see his passion and his pain. I believe that after his confrontation by Jesus on the road to Damascus he abandoned the sterile form of religion that had suffocated his heart for so many years and was himself transformed into the kind of person that he is urging his readers to become. He had learned to truly live from his heart and be led by the Spirit of God. That always involves in some way sharing in the intense passion of God for salvaging everyone possible back into an intimate and synchronized, life-giving, thriving relationship with God, our Lover and Creator.
Therefore I urge you, brethren...
What is the identity of those he is addressing here?
But he is a Jew who is one inwardly; and circumcision is that which is of the heart, by the Spirit, not by the letter; and his praise is not from men, but from God. (Romans 2:29)
Nor are they all children because they are Abraham's descendants, but: "THROUGH ISAAC YOUR DESCENDANTS WILL BE NAMED." That is, it is not the children of the flesh who are children of God, but the children of the promise are regarded as descendants. (Romans 9:7-8)
So all Israel will be saved; (Romans 11:26)
So these also now have been disobedient, that because of the mercy shown to you they also may now be shown mercy. For God has shut up all in disobedience so that He may show mercy to all. (Romans 11:31-32)
This urging is to all who will believe and respond. And those who do respond compose what God views as Israel who will be saved. If you confess with your mouth Jesus as Lord, and believe in your heart that God raised Him from the dead, you will be saved. (Romans 10:9)
There is so much more packed in this verse that I plan to continue unpacking it for some time. But this is a start.