The seed (Hebrew "zera" figuratively for posterity or literally for child) of Abraham is Isaac born out of God's promise to him through his beloved wife, a freewoman Sarah. Isaac was born out of God's covenant and not by a man's decision. As the word "seed" singular is used and not plural "seeds", it refer to one child or descendant. Literally speaking the seed refers to Isaac and figuratively it points forward to Jesus Christ.
The seed in these 2 verses means, Hebrew "zera" for child or posterity.
Gen 15:3 And Abram said, Behold, to me thou hast given no seed: and, lo, one born in my house is mine heir.
Gen 17:19 And God said, Sarah thy wife shall bear thee a son indeed; and thou shalt call his name ISAAC: and I will establish my covenant with him for an everlasting covenant, and with his seed after him.
As the seed has figuratively meaning, Apostle Paul points it towards Jesus Christ.
Gal 3:16 (Apostle Paul wrote) 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 3:14 That the blessing of Abraham might come on the Gentiles through Jesus Christ; that we might receive the promise of the Spirit through faith.
There are several Abrahamic covenants found in Genesis 12-17. From these covenants, God promises:
- To make of Abraham a great nation, and to bless those who bless him and curse those who curse him (Gen 12:1-3) --It was during God's calling for Abraham to leave Haran for Canaan
- To give Abraham's descendants all the land from the river of Egypt to the great river Euphrates (Gen 15:18-21)
- To make Abraham a father of a great many nations, to give him and his offspring all the land of Canaan for an everlasting possession, and to be his God and to the offspring after him (Gen 17:1-8)
- To give Abraham and his seed (posterity) circumcision as the permanent sign of this everlasting covenant, to Ishmael 12 princes & great nation and to Isaac the everlasting covenant for his offspring after him (Gen 17:9-22)
First time God said to Abraham in Genesis 12:1-3 and appeared to him in Gen 12:7. Second time God was covenanting with him in a vision Gen 15:1-18. Third time God appeared to Abraham and was covenanting with him all the way from Gen 17:1-22. As God was still speaking to Abraham, the covenant was with him and not with Ishmael nor Isaac. Hence in Gen 17:21 God was covenanting with Abraham "But my covenant will I establish with Isaac..." -- a promise when he was not yet born. The promise of land to Jacob son of Isaac, was fulfilled in Genesis 28:13.
Gen 17:7 & 8 (YHWH said to Abraham) And I will establish my covenant between me and thee and thy seed ... all the land of Canaan, for an everlasting possession; AND I (YHWH) will be their GOD.
Gen 17:19 And God said, Sarah thy wife shall bear thee a son indeed; and thou shalt call his name Isaac: and I will establish my covenant with him for an everlasting covenant, and with his seed after him.
Gen 17:21 But my covenant will I establish with Isaac -- a promise when he was not yet born. Abraham was 99 years old (Gen 17:1), Ishmael 13 (Gen 16:16) and Sarah 89 (Gen 17:17).
YHWH only stopped talking with Abraham and departed from him in Gen 17:22.
Gen 21:12But God said unto Abraham "... for in Isaac shall thy seed (posterity/offspring) be called (chosen)". It is clearly stated that the chosen posterity is Isaac.
Clue, covenant includes (Gen 17:8) "I (YHWH) will be their GOD".Gen 28:13 And, behold, the LORD stood above it, and said, "I am the LORD God of Abraham thy father, and the God of ISAAC: the land whereon thou liest, to thee will I give it, and to thy seed"
Ishmael did not inherit the land in Canaan as told in Gen 25:17. If Ishmael was in the Abrahamic covenant with a promise of land of Canaan and yet died in a Gentile land Egypt, then YHWH had broken the covenant. Refer(Gen 17:8) "I (YHWH) will be their GOD".
Gen 25:17And these are the years of the life of Ishmael, a hundred and thirty and seven years: and he gave up the ghost and died; and was gathered unto his people. Gen 25:18 And they dwelt from Havilah unto Shur, that is before Egypt (Gentiles nation), as thou goest toward Assyria: and he died in the presence of all his brethren. Isaac died in Hebron Gen 35:27-29 in the promised land of Canaan, an ancient term for a region encompassing present-day Israel, the West Bank, and the Gaza Strip, plus adjoining coastal lands and parts of Lebanon and Syria.
Gen 17:8 "I (YHWH) will be their GOD". The covenant goes with the bloodline of Abraham whom YHWH declares "I am the God of Abraham, the God of Isaac, and the God of Jacob". One cannot find a single verse in the Bible "I am the God of Abraham, the God of Ishmael, the God of Nebajoth (Gen 25:13)"
No doubt Abrahamic Covenant goes with Isaac as YHWH declared "I am the God of Isaac"
Exo 3:15And God (YHWH) said moreover unto Moses, Thus shalt thou say unto the children of Israel, The LORD God of your fathers, the God of Abraham, the God of ISAAC, and the God of Jacob, hath sent me unto you: this is my name forever, and this is my memorial unto all generations.
Gen 16:1 Now Sarai Abram's wife bore him no children: and she had an handmaid, an Egyptian, whose name was Hagar.
Gen 16:15 And Hagar bore Abram a son: and Abram called his son's name, which Hagar bore, Ishmael.
Hagar was an Egyptian slavewoman (a Gentile) Gen 21:9 and not a freewoman. Could a son of slavewoman inherit everlasting covenant when the son was cast out (Gen 21:10)?
Abraham died at age of 175 years and buried at east of Mamre (Gen 25:7-9)or Kiriath-arba that is, Hebron, where Isaac was also buried (Gen 35:27-29)
Gen 25:8Then Abraham gave up the ghost, and died in a good old age, an old man, and full of years; and was gathered to his people.
Gen 25:9And his sons Isaac and Ishmael buried him in the cave of Machpelah, in the field of Ephron the son of Zohar the Hittite, which is before Mamre
Gen 21:9And Sarah saw the son of Hagar the Egyptian, which she had born unto Abraham, mocking.
Gen 21:10Wherefore she said unto Abraham, Cast out this bondwoman and her son: for the son of this bondwoman shall not be heir with my son, even with Isaac.
Gal 4:30Nevertheless what saith the Scripture? Cast out the bondwoman and her son: for the son of the bondwoman shall not be heir with the son of the freewoman.
YHWH did fulfil the covenant with Abraham regarding his son Ishmael. It was to make Ishmael's descendants a great nation but no promise of the land for him and his seed.Gen 17:20 And as for Ishmael, I have heard thee: Behold, I have blessed him, and will make him fruitful, and will multiply him exceedingly; twelve princes shall he beget, and I will make him a great nation.
Gen 25:13And these are the names of the sons of Ishmael, by their names, according to their generations: the firstborn of Ishmael, Nebajoth; and Kedar, and Adbeel, and Mibsam,
Gen 25:14And Mishma, and Dumah, and Massa,
Gen 25:15Hadar, and Tema, Jetur, Naphish, and Kedemah:
Gen 25:16These are the sons of Ishmael, and these are their names, by their towns, and by their castles; twelve princes according to their nations.
Gen 25:17And these are the years of the life of Ishmael, a hundred and thirty and seven years: and he gave up the ghost and died; and was gathered unto his people.
Gen 25:18And they dwelt from Havilah unto Shur, that is before Egypt, as thou goest toward Assyria: and he died in the presence of all his brethren.
Ishmael died in Egypt (Gentiles nation) for sure (Gen 25:17-18); Abraham and Ishmael never enter Arabia and built Kaabah in Mecca (Sura 2:125).Did God (YHWH) break the covenant with Abraham when Ishmael died in Egypt but not in the promised land of canaan? Nay, Rom 3:4 God forbid: yea, let God be true, but every man a liar.
First Witness: Prophet Moses
Gen 17:9 And God said unto Abraham, "Thou shalt keep my covenant therefore, thou, and thy seed after thee in their generations
Gen 17:20-21 And as for Ishmael, I have heard thee: Behold, I have blessed him, and will make him fruitful, and will multiply him exceedingly; twelve princes shall he beget, and I will make him a great nation. But my covenant will I establish with Isaac..."
Second Witness: Apostle Paul
Galations 4:30 Nevertheless what saith the Scripture? Cast out the bondwoman and her son: for the son of the bondwoman shall not be heir with the son of the freewoman.
Galations 4:31 So then, brethren, we are not children of the bondwoman, but of the free.
The matter has been established that God's Covenant with Abraham goes with the bloodline of Isaac by the mouth of 2 witnesses. God's law requires only 2 or 3 witnesses to put a man to death just as Lord Jesus was crucified by the testimony of 2 false witnesses (Matt 26:60). The obvious truth is that Isaac was the promised offspring.
References on Mosaic law
Deu 17:6 (YHWH said:) At the mouth of two witnesses, or three witnesses, shall he that is worthy of death be put to death; but at the mouth of one witness he shall not be put to death.
2Co 13:1 (Apostle Paul) This is the third time I am coming to you. In the mouth of two or three witnesses shall every word be established.
Mat 18:16 (Lord Jesus said) But if he will not hear thee, then take with thee one or two more, that in the mouth of two or three witnesses every word may be established.