Sarai approached Abram with a solution to the promise because, at 75 years of age, she had no child, and no hope of having one, and so as far as she was concerned there must be a seed to Abram. From his loins must come the seed through whom the promise will be given.
We see this constantly today. We see the church going to the world for its methods, its conduct. We hear today of people who are doctrinally conservative, but culturally progressive. Doctrinally they believe the Reformed faith, or say they do, and follow the word of God and preach it, but culturally they are ready to adopt the customs of the world in the interests of Christian work and evangelism, feeling they can make a greater noise that way. Now is this allowable in the Bible or not, or is it a matter of principle that we should avoid this? Well it is a matter of principle, because throughout the Book of Genesis, this is the repeated story: that every time the culture of the seed of the serpent, of the world, is adopted, no matter how good the intentions, no matter the right beliefs, it is wrong and it leads to disaster. Today we have even celebrity Bible teachers, and people say, ‘How wonderful they are, and how wonderful their expositions are.’ But things which are so prominent in the Scripture, these wonderful celebrities seem to fail altogether to see. If you compromise with the world and its methods and you become culturally progressive; you disobey God and you are in serious trouble. You are locked into trusting him, no matter how bleak the situation is, and his word and his methods. There was hostility from the seed of the serpent toward the seed of the woman, the people of God, and you cannot mix the two together. Here Abram and Sarai are not only going to mix them together; they are going to say to an Egyptian girl and a slave in their household, ‘Comes right into the family. We will make you, in a sense, a very prominent person in the church, because you can do something for us we cannot otherwise do. Here you have got a classic case of the church and the world being mixed together. The principle gets missed.