Abel had an undivided heart, a heart just for God. Cain - well, he is in the line of Saul. If we were going out of the Pentateuch into the other books, we should come unto David and Saul as a pair. We would see the divided heart of Saul and the undivided heart of David. We also see Abraham and Lot, Abraham as a man with the undivided heart and Lot as a man who had interests in this world other than God's. Lot's own interests revealed his divided heart.
Then we see Isaac and Ishmael, and their history, as well as this spiritual principle, declares the difference between them. Isaac had his very existence on the basis of an intervention from heaven, on the basis of the power of resurrection from the dead. His beginning is wholly of God, and he lives a quiet life. You may find some fault with Isaac, but the fact is that he is just there.
Now that may be a very good thing. It might be possible that you are just there. You may not be an Abraham. You may not be a David. You may not be one of these great ones, but you can be there walking up and down in the land. Does it mean that because you are just here on the earth that you have no significance? By his very presence on earth, Isaac signifies the Almighty power of God: he signifies the supernatural behind his very existence for he is the embodiment of the power of resurrection.
Read your New Testament in that connection. In the Letter to the Hebrews, it says that Abraham's body was now "as good as dead," but he believed that God was able to raise him from the dead. You say, "Well, I have no public ministry." You may have had, and the Lord may have asked you to just lay it down. You may not be a very prominent person in the Christian world of whom people are taking note, but you are here holding the ground for God and standing on the ground of God's absolute ability to keep you alive when naturally it would not be so. Do not think that because you are an Isaac that you do not count as much as the others. You are "just there" walking up and down in the land, opening the wells.