Gen 22:2 And he said, Take now thy son, thine only son Isaac, whom thou lovest, and get thee into the land of Moriah; and offer him there for a burnt offering upon one of the mountains which I will tell thee of.
In the Bible are many what we would call contradictory statements, yet each can be fully harmonized as we properly consider what they mean. Take Isaac being referred to as the only son of Abraham for example. We know that Abraham had more than one son, and even that Ishmael was fathered by Abraham before Isaac. So in what sense is Isaac Abraham’s only son.
There are couple of senses, the first being that Isaac was a type of Christ, the only begotten son of God, and to properly typify this, Isaac also must be considered an only son. Knowing of other sons means that Isaac was not an only son by generation, but by the promise. Therefore, Isaac is also typical of the child of God, and as such receives the blessing simply because of the promise of God. As the receiver of the promise which was fathered in Abraham (Rom 4:11), Isaac was then given all that Abraham had (Gen 24:36). Sure Abraham gave gifts to his other children by generation (Gen 25:6), but the gifts were comparatively small in light of that which he had passed down to Isaac, which because it had eternal value was considered ALL (Gen 25:5).
In relation to the type of Christ, Abraham as father was willing to sacrifice his own son even though the covenantal promise of God must come through Isaac (Gen 17:19), thereby believing that God was able to raise him from the dead to fulfill the promise (Heb 11:19). The Lord in mercy took Abraham`s will for the deed and provided Himself a substitutionary sacrifice (Gen 22:12-13). In this the Lord showed that if even a man can be willing to put his own son on the altar, then may God not do much more on the behalf of men?
In relation to the type of the child of God, Isaac is considered an only son when the inheritance is passed out. Sure before the time of the inheritance the children received gifts, but these gifts were temporal, and had no eternal value. Likewise today, in a certain sense God is the Father of all mankind, for without his making us a living soul (Gen 2:7) none of us would live. In this he provides some basic gifts in varying measure to all mankind (yes even to those who hate Him), basic things such as food, water, air, etc. and even some special gifts like happiness, and personal safety; all of which are temporal in nature. They are gifts that can be used now, but are of no use in eternity. The child of God however takes the gifts and continues on to receive the promise by faith, thereby ensuring that when the eternal inheritance is passed out, they will receive ALL that the Father has to give. Being a child of the promise qualifies one to receive the only things of real lasting value. The gifts of earth are temporal, but the ‘ALL’ that is truly valuable that the Father has to give for eternity, is reserved for those who have become the children of God by faith.
It is in this sense Isaac who was considered an only son because of the promise of God, received ALL that his father had to give. It is in this sense that the Christian who though troubled in this world, becomes an heir of the promise in the next world through faith in the Son, and inherits ALL that the Father has to give for eternity!
Gen 25:5 And Abraham gave all that he had unto Isaac.