| Barnes' Notes on the Bible Isaac and Ishmael - Isaac, though younger than Ishmael, is placed first, as the legitimate heir, since Sarah alone was Abraham's true wife (compare the 1 Chronicles 1:36 note).
Gill's Exposition of the Entire BibleThe sons of Abraham,.... The famous and well known ancestor of the Jews; of Ishmael his firstborn, and his posterity; of his sons by Keturah; and of Isaac and his sons, an account is given from hence to the end of 1 Chronicles 1:34 entirely agreeing with that in Genesis 25:1.
Keil and Delitzsch Biblical Commentary on the Old TestamentThe sons of Abraham. - In 1 Chronicles 1:28 only Isaac and Ishmael are so called; Isaac first, as the son of the promise. Then, in 1 Chronicles 1:29-31, follow the posterity of Ishmael, with the remark that Ishmael was the first-born; in 1 Chronicles 1:32 and 1 Chronicles 1:33, the sons of Keturah; and finally in 1 Chronicles 1:34, the two sons of Isaac.
Geneva Study BibleThe sons of Abraham; Isaac, and Ishmael.
Wesley's Notes 1:28 The sons of Abraham - All nations but the seed of Abraham are already shaken off from this genealogy. Not that we conclude, no particular persons of any other nation but this found favour with God. Multitudes will be brought to heaven out of every nation, and we may hope there were many, very many people in the world, whose names were in the book of life, tho' they did not spring from the loins of Abraham.
Matthew Henry's Concise Commentary28-54 The genealogy is from hence confined to the posterity of Abraham. Let us take occasion from reading these lists of names, to think of the multitudes that have gone through this world, have done their parts in it, and then quitted it. As one generation, even of sinful men, passes away, another comes. Ec 1:4; Nu 32:14, and will do so while the earth remains. Short is our passage through time into eternity. May we be distinguished as the Lord's people. | 
