Sara, Abraham's wife, did not believe in the promise that she would conceive Isaac at first. She had been barren for many years, and despite the prayers of her and Abraham the Lord had not yet answered them and given them a child together.
We can think of so many things in our own lives. If it is in the word of God and it is promised, it will be kept. If God promises to sustain us and to use us as his instruments and if we keep the terms, then those promises will be kept. If you are a seeker after Christ, you sometimes wonder, ‘Yes, I repented, and I asked Christ to bless me and to make me his own, but will he hear me? Is his promise to me?’ Well, the terms of the Scripture are unconditional. If you are sincere in your heart, and you believe in Christ, and you repent of your sin, then he will forgive you and bless you. He is bound to keep his promise. Set your mind to work when faith is overwhelmed. Who has promised? Have I been reading the Scripture? Do I keep a note of the great promises of God? I think of his attributes, I think of all the evidences since I was saved in my life of answered prayer. Do you remember them? Do you reflect on them and think about them? I know that he has a purpose.
Christian people, believers in the Lord, should promote gratitude and trust and faith but you see a number of principles in the experience of Sarah. God renewed her faith. She had to exercise it and she did and she trusted God, who had promised. If God is going to use us in his service and bring people into the kingdom through our instrumentality, then faith is required. You might say that the miracle of conception special conception did not take place with Abraham and Sarah until faith was being exercised, until they trusted him.
Why did God keep them waiting so long for a child? I remember years ago that this was something that puzzled me. ‘What a strange thing for God to do’, I thought rather irreverently. ‘What a curious thing that God should keep them waiting until they were 90 and 100 years old before the promised child came. Why was that? I used to think that maybe it was just a refining of their faith. Well no doubt that was a part of it, but only a small part in a way. God had a purpose, and he kept that purpose secret, but it is obvious now, with hindsight. It was to show future generations that the calling of the Jews for that dispensation, and the coming of Christ ultimately, were special acts of God. They could not have happened in the ordinary course of events. It wasn't enough as far as God was concerned for Abraham and Sarah to have a child in the ordinary course of events. That child, and the line flowing from that child, would be a nation that was selected as a demonstration of God's power and to bring in the Saviour. Isaac was to be a child in fulfilment of the promise, a child given by supernatural intervention, not a child conceived and born in the natural way as Ishmael. In this way he is a type of everyone who is born ‘not of blood, nor of the will of the flesh, nor of the will of man, but of God’ (John 1:13).
Does God still speak to his people today? Now God did not communicate to Abraham in a way whereby Abraham could have been mistaken. He appeared to him, God does not deal with people in this way today. Now we have the complete and perfect revelation of his word. We have all the truth revealed. God does deal with individuals but in a different way. He may remind us of things we already know. He may move our consciences. He may remind us very keenly of our duties or are calling in some situation, but he no longer reveals to us authoritative truth in a personal manner or great things because they're all in the word. This is final and all sufficient for us.