Genesis 17:19

“And God said, Sarah thy wife shall bear thee a son indeed, etc.] This is repeated for the confirmation of it, and thus expressed to remove all doubt about it, if any there were, that hung upon Abraham’s mind; as well as to let him know that the promise of a son by Sarah was not to be superseded by his prayer for Ishmael, for whom he might have a greater flow of natural affection than for his unborn son, in whom his seed should be called: and thou shall call his name Isaac; which signifies “laughter”; and which name was given him from the laughter of Abraham at the promise of him, and not from the laughter of Sarah, which as yet was not; wherefore Josephus f1094 is wrong when he suggests,…”

“The blessings of the covenant are reserved for Isaac, but common blessings were abundantly promised to Ishmael; and though the visible Church did not descend from his family, yet personally he might, and it is to be hoped did, enjoy its benefits. Next: Genesis Chapter 18”

“- The Sealing of the Covenant 1. שׁדי shaday, Shaddai, “Irresistible, able to destroy, and by inference to make, Almighty.” שׁדד shādad “be strong, destroy.” This name is found six times in Genesis, and thirty-one times in Job. 5. אברהם 'abrâhām, Abraham, from אברם 'abrām “high-father,” and הם hām the radical part of המין hāmôn a “multitude,” is obtained by a euphonic abbreviation אברהם 'abrâhām, “father of a multitude.” The root רהם rhm is a variation of רום rvm; affording, however, a link of connection in sound and sense with the root המה hāmâh “hum, be tumultuous,” from which comes המון hāmôn a “multitude.” The confluence of the biliterals רם rm and הם hm yields the…”

“17:19 The name Isaac (Hebrew yitskhaq, “he laughs”) would constantly recall Abraham’s disbelieving laughter when he heard the promise. It was also a reminder of God’s favor and his pleasure in the birth (cp. 21:6).”