There was given to Abraham the promise, especially dear to the people of that age, of a numerous posterity and of national greatness: “I will make of thee a great nation, and I will bless thee, and make thy name great; and thou shalt be a blessing.” And to this was added the assurance, precious above every other to the inheritor of faith, that of his line the Redeemer of the world should come: “In thee shall all families of the earth be blessed.”—Patriarchs and Prophets, 125.
When Abraham was nearly one hundred years old, the promise of a son was repeated to him, with the assurance that the future heir should be the child of Sarah. But Abraham did not yet understand the promise. His mind at once turned to Ishmael, clinging to the belief that through him God’s gracious purposes were to be accomplished.... Again the promise was given, in words that could not be mistaken: “Sarah thy wife shall bear thee a son indeed; and thou shalt call his name Isaac; and I will establish my covenant with him.” ...
The birth of Isaac, bringing, after a lifelong waiting, the fulfillment of their dearest hopes, filled the tents of Abraham and Sarah with gladness.—Patriarchs and Prophets, 146.
“And Sarah said, God hath made me to laugh ... for I have born ... a son.” Genesis 21:6, 7.
Isaac was her joy and pride; her life was bound up in him.—Patriarchs and Prophets, 151. RRe 277
I was shown that the law of God would stand fast forever, and exist in the new earth to all eternity. At the creation, when the foundations of the earth were laid, the sons of God looked with admiration upon the work of the Creator, and all the heavenly host shouted for joy. It was then that the foundation of the Sabbath was laid. At the close of the six days of creation, God rested on the seventh day from all His work which He had made; and He blessed the seventh day and sanctified it, because that in it He had rested from all His work. Hvn 142
And Sarah said, God hath made me to laugh, so that all that hear will laugh with me. Genesis 21:6. KJV