John Gills Exposition of the Bible Commentary - Genesis 17:18
And Abraham said unto God ,.... Being told he should have a son by Sarah, that should be his heir, he is concerned for Ishmael what would become of him; and who, being grown up, had doubtless a large share in his affections, and it is highly probable he began to think he was the promised seed, since he had lived to such an age, and had no other son, and Sarah was past bearing children: but now perceiving it would be otherwise, he puts up a petition for Ishmael, whom he did not neglect upon... read more
Matthew Henry's Complete Commentary - Genesis 17:15-22
Here is, I. The promise made to Abraham of a son by Sarai, that son in whom the promise made to him should be fulfilled, that he should be the father of many nations; for she also shall be a mother of nations, and kings of people shall be of her, Gen. 17:16. Note, 1. God reveals the purposes of his good-will to his people by degrees. God had told Abraham long before that he should have a son, but never till now that he should have a son by Sarai. 2. The blessing of the Lord makes fruitful, and... read more