Not however that God's word has failed; for all who have sprung from Israel do not count as Israel,
nor because they are Abraham's true children. But the promise was "Through Isaac shall your posterity be reckoned."
In other words, it is not the children by natural descent who count as God's children, but the children made such by the promise are regarded as Abraham's posterity.
For the words are the language of promise and run thus, "About this time next year I will come, and Sarah shall have a son."
Nor is that all: later on there was Rebecca too. She was soon to bear two children to her husband, our forefather Isaac--
and even then, though they were not then born and had not done anything either good or evil, yet in order that God's electing purpose might not be frustrated, based, as it was, not on their actions but on the will of Him who called them, she was told,
"The elder of them will be bondservant to the younger."
This agrees with the other Scripture which says, "Jacob I have loved, but Esau I have hated."
What then are we to infer? That there is injustice in God?
No, indeed; the solution is found in His words to Moses, "Wherever I show mercy it shall be nothing but mercy, and wherever I show compassion it shall be simply compassion."
And from this we learn that everything is dependent not on man's will or endeavour, but upon God who has mercy. For the Scripture said to Pharaoh,