I beg the Reader, to observe with me, that the great object in the Chronicles being to preserve in the mind the lineal descent from Adam to Christ, the sacred Writer, in this instance, as in the instance before in the race of Noah, first dismisses in a short way the stock of Abraham, after the ordinary course of nature, to dwell more largely hereafter on the seed according to grace. Hence the children of Ishmael, are taken notice of before those of Isaac.
1 Chronicles 1:28-33
28 The sons of Abraham; Isaac, and Ishmael.
29 These are their generations: The firstborn of Ishmael, Nebaioth; then Kedar, and Adbeel, and Mibsam,
30 Mishma, and Dumah, Massa, Hadad,e and Tema,
31 Jetur, Naphish, and Kedemah. These are the sons of Ishmael.
32 Now the sons of Keturah, Abraham's concubine: she bare Zimran, and Jokshan, and Medan, and Midian, and Ishbak, and Shuah. And the sons of Jokshan; Sheba, and Dedan.
33 And the sons of Midian; Ephah, and Epher, and Henoch, and Abida, and Eldaah. All these are the sons of Keturah.