The Lord was not done with Abraham after Hagar begat him Ishmael. Thirteen long years after Ishmael was born, the Lord visited Abraham - again. The Lord is gracious indeed! Abraham’s faith rose again. Therefore sprang there even of one, and him as good as dead, so many. – Heb 11:12. Eventually, Sarah conceived by Abraham and bore the son of promise Isaac at the set time of which God had spoken to him – Gen 21:2. Through faith also Sara herself received strength to conceive seed, and was delivered of a child when she was past age, because she judged Him faithful who had promised. – Heb 11:11.

Isaac was born. The believing line was on!

Soon afterward, God wanted to test the genuineness of the faith of Abraham – not only for his sake but also that his children of faith might learn a valuable lesson from this episode. God said, “Take now thy son, thine only son Isaac, whom thou lovest, and get thee into the land of Moriah; and offer him there for a burnt offering upon one of the mountains which I will tell thee of”. – Gen 22:2.

The Serpent must have been overjoyed at the imperative – Is God putting an end to His own plan? Is God walking off from his purpose? Satan didn’t know that God was working out His plan as charted out originally. This event would have very-long term implications. All those who believe in Him will be encouraged by the faith of Abraham; this incident would contribute hugely to the Eternal Hope of the people of God. More importantly, it was a shadow of what God was intending to do in His-story. The Seed of the woman, the Son of God would be offered as a once-and-for-all sacrifice for the sin of the world but would rise again from his death. This would further lead to the resurrection to eternal life of the believers.

Isaac asked Abraham, “Behold the fire and the wood: but where is the lamb for a burnt offering? And Abraham said, “My son, God will provide Himself a lamb for a burnt offering”. Gen 22:7. YHWH YIREH! Seeing the need of His people, the Lord will provide! (ஈவாரே?) Jehovah-Jireh!

By faith Abraham, when he was tried, offered up Isaac: and he that had received the promises offered up his only begotten son, of whom it was said, that in Isaac shall thy seed be called: Accounting that God was able to raise him up, even from the dead; from whence also he received him in a figure. – Heb 11:17.

The Serpent was disappointed and alarmed as well. Isaac, the promised son, is a threat to his existence.
We need to take note of the singular noun “seed” which is clarified later in the scriptures.
The Lord swore by Himself to Abraham, “And in thy seed shall all the nations of the earth be blessed; because thou hast obeyed my voice.” – Gen 22:18.

The Lord spoke to Isaac, Abraham’s son of the promise, “And I will make thy seed to multiply as the stars of heaven, and will give unto thy seed all these countries; and in thy seed shall all the nations of the earth be blessed;” – Gen 26:4.

The Lord confirmed to Jacob, Abraham’s grandson, “And thy seed shall be as the dust of the earth, and thou shalt spread abroad to the west, and to the east, and to the north, and to the south: and in thee and in thy seed shall all the families of the earth be blessed”. – Gen 28:14.

“Now to Abraham and his seed were the promises made. He saith not, and to seeds, as of many; but as of one, and to thy seed, which is Christ.” – Gal 3:16. That the blessing of Abraham might come on the Gentiles through Jesus Christ; – Gal 3:14. It is this Jesus Christ who was to be born the Seed of the woman later in His-story.

Gentiles are non-Jews and include all the people of the world. Everyone who believed/believes in the promise of God is counted as a believer and is blessed. It is about these people God said, “And if ye be Christ's, then are ye Abraham's seed, and heirs according to the promise”. – Gal 3:29. These are the innumerable stars in the heaven that God showed to Abraham (then Abram).

While the believing population was denoted by the innumerable stars in the sky, the dust of the earth was the rest of the offspring of Abraham – the unbelieving lot. It is was never about Jews and Muslims by religion.
Abraham sent his servant to bring a bride for Isaac from his native Mesopotamia. Rebekah was the bride. And Isaac brought her into his mother Sarah's tent, and took Rebekah, and she became his wife; and he loved her: - Gen 24:67.

Then again Abraham took a wife, and her name was Keturah. – Gen 25:1. And she bore him children. And Abraham gave all that he had unto Isaac. – Gen 25:5. But unto his other children, “Abraham gave gifts, and sent them away from Isaac his son, while he yet lived, eastward, unto the east country. - Gen 25:7. These might also be the ones who migrated to the Indus, Yang Tse, and You Kong valleys to establish civilizations.
The Dragon could not let things continue like this. Would the firstborn of Isaac be the one that would bring an end to Satan’s existence? How could he remain slack in his attempt to foil the plan of God?

The Serpent was quick to identify his next weapon. Esau. Esau being the first-born could be the important link to the Seed of the woman. So, trapping him into his fold would upset the purpose of God. Satan quickly won Esau to his side and as his seed, he became the arm that Satan would use to put an end to the purpose of God.

By faith, Isaac blessed Jacob and Esau concerning things to come. – Heb 11:20. Jacob and Esau? Was not Esau the firstborn? Yes. But God is all-knowing. He has foreknown His children. And Esau was not in the believing line. Jacob was. Esau was Satan’s seed.