Prior to chapter fifteen, Abraham had experienced God as the One who protected him and provided many material things (12:16). Abraham had given all the choices to Lot and had gained the victory over the four kings. None of these things, however, had anything to do with the fulfillment of God's purpose but were only related to Abraham's existence (12:10; 14:24). He experienced all these outwardly in his environment, not inwardly in his life.
Do you know what God's purpose is? God's purpose is to have a people to express Him with His image, represent Him with His dominion, and take the earth for His kingdom. Beginning with Genesis 1:26, we see that God's eternal purpose is to have a people expressing Him in His image, representing Him with His dominion, and taking over the earth for His kingdom. When God came in to call Abraham He promised Abraham that he would have the blessing to express God and become a great nation so that through him God might have His kingdom on earth. This is God's eternal purpose today. But everything that had happened to Abraham prior to Genesis 15 had nothing to do with the fulfillment of God's purpose. It is from chapter fifteen through chapter twenty-four that we have a record showing us how God had worked something into Abraham so that he was able to fulfill God's purpose. It was no longer merely outward experiences in environment but inward experiences in life.
Most Christians today only care for their existence, not for God's eternal purpose. Even many among us still have not been deeply impressed with God's eternal purpose. Many are still hoping that the Lord will give them a better job, a good husband or wife, a good education, or an excellent promotion. While all of these things may enable you to exist, they have nothing to do directly with the fulfillment of God's purpose. Everything prior to chapter fifteen was good, helpful, and profitable for Abraham's existence, enabling him to live as a human being, but none of those things had anything to do directly with the fulfillment of God's purpose. Look into Abraham's situation. Could the cattle that Abraham gained in Egypt express God? Could the maidservants represent God? Although God had given Abraham a great deal, nothing that he had was useful for the fulfillment of God's purpose. To exist is one thing, and to fulfill God's purpose is another. The principle is the same with us today. Our education, jobs, and houses are all good for our existence, but none of them are good for the fulfilling of God's purpose.
Now we need to see the two things that were necessary for the fulfillment of God's purpose in Abraham's day. The first item was the seed (15:1-6; see 13:16; 22:17-18; 12:2). God called Abraham with the intention of fulfilling His purpose. As we have seen, His purpose is to have a people in His image to express Himself and with His dominion to represent Himself. But Abraham did not have a seed. How could Abraham fulfill God's purpose without having a seed? God needs the seed. He needs to have a people through the seed.