grounds of assurance - D. Martyn Lloyd-Jones

“but God shows His love for us in that while we were still sinners, Christ died for us. Since, therefore, we have now been justified by his blood, much more shall we be saved by him from the wrath of God. For if while we were enemies we were reconciled to God by the death of his Son, much more, now that we are reconciled, shall we be saved by his life.” Romans 5:8-10

“Apostle Paul wants these people to rejoice in their salvation and ‘the hope of the glory of God’, and He show that they will only rejoice in it as they understand and grasp God’s great love to them. That is why I say that this demonstration, this proof of the love of God, is one of the profoundest sources of assurance that one can ever have.
How does this gratuitous element in our salvation provide me with grounds of assurance? Let me put it like this. Imagine what the position would be if our salvation were not entirely of grace. If, for instance, I believed that Christ had died for me because I loved God, and because I was trying to please God, and because I was a good man who was striving to keep the Law, and who had succeeded up to a point, if I believed that my salvation was the result of the fact that I was such a good man, then the inevitable corollary would be, that I would say to myself, “What if in the future, sometime or another, I should love God less, what if I failed to keep His Commandments, what if I failed to seek God and to please Him and to live for Him as I have been doing in the past? If my salvation depends upon what I am, and what I have done, and what I desire, if it in any sense depends upon me, what security have I got? I may change, I may falter, I may fail.’
If our salvation depended in any sense, or to any extent at all, upon ourselves, our position would always be precarious. We might fail at any moment and would then lose all. But, thank God, says the Apostle, that is not the position. Our salvation in no respect at all depends upon ourselves, it is entirely dependent upon the love of God. And because my salvation depends upon the love of God and on that alone, and on nothing in me, I am sure of it, I am certain of it. Why? Because God does not change, and cannot change, and if I am within the ambit and the scope of the love of God now, I always shall be. The love of God, the gratuitous character of my salvation, my realization that I was without strength, that I was ungodly, a sinner, and that it is entirely in spite of me that Christ died for me, these are the ultimate ground of my assurance. And on this ground I am assured, not only that I am saved now, but that I shall remain saved, that because I am justified I am also glorified, and therefore I rejoice in hope of the glory of God.”

- D. Martyn Lloyd-Jones, Romans: Assurance, Exposition of Chapter 5