To whom was this covenant-promise later renewed?

Answer

"And God said unto Abraham, . . . Sarah thy wife shall bear thee a son indeed; and thou shall call his name
Isaac:- and I will establish My covenant with him for an everlasting covenant, and with his seed after him."
"I will make thy seed to multiply as the stars of heaven. . . . and in thy seed shall all the nations of the earth
be blessed." Gen. 17: 15-19; 26: 4.

By whom was this fulfilled?
What is necessary in order that the preaching of the gospel may be profitable?
What is the only unpardonable sin?
What is the ground of justification on God's part?
What great truth therefore follows?
How early does Paul say Timothy was instructed?
What prophecy had Paul upon which to base his statement?

Questions & Answers are from the book Bible Readings for the Home Circle