Genesis 17 The Covenant is to be through Isaac because Abram fell on the floor laughing when G_d told him he would have a son. See vs15-22 (Isaac = laughing)
See also 17:7-8 Land covenant repeated and, later, genealogical / circumcision covenant. The two are made one through Isaac.
Not sure I understand all your intent here but..I will answer to some points I think might help to at least see my views of this.
The land was spoken of before Gen 15 and 17. Not given in covenant until Gen 15 and 17.
Gen 15 is not when God gave the land to the fathers. Rather it was to his seed of the 4th generation. Abraham is said to die and be buried in this covenant. I see it more as Abraham is given the promise of heirs.
Abraham is not personally promised the land until gen 17.
These two things (or covenants) bring in the need for a resurrection from the dead. Since Abraham is told the 4th Generation will inherit and he will die before he inherits the land.
Gen 15:15 And
thou shalt go to thy fathers in peace; thou shalt be buried in a good old age.
16 But in the
fourth generation they shall come hither again: for the iniquity of the Amorites is not yet full.
17 And it came to pass, that, when the sun went down, and it was dark, behold a smoking furnace, and a burning lamp that passed between those pieces.
18 In the same day
the LORD made a covenant with Abram, saying, Unto thy seed have I given this land, from the river of Egypt unto the great river, the river Euphrates:
It was not until gen 17 that Abraham, Isaac, and Jacob, the patriarchs are given promise in covenant.
Since Abraham knew they were going to be dead by the time they inherited it, his faith was tested with Isaac. Abraham expected God to raise him from the dead. The promise of the resurrection was established in Isaac.
Waiting for the promise to the fourth generation...We have the same here.
Third generation dies...….
Ge 50:23 And Joseph saw Ephraim’s children of the
third generation: the children also of Machir the son of Manasseh were brought up upon Joseph’s knees.
Ex 1:6 And
Joseph died, and
all his brethren, and
all that generation.
Joseph having faith in the resurrection..
Ge 50:25 And Joseph took an oath of the children of Israel, saying,
God will surely visit you, and ye shall carry up my bones from hence.
Ex 13:19 And
Moses took the bones of Joseph with him: for he had straitly sworn the children of Israel, saying,
God will surely visit you; and ye shall carry up my bones away hence with you.
Acts 7 and Hebrews 11 speak of this.
Act7:2 And he said, Men, brethren, and fathers, hearken; The God of glory appeared unto our father Abraham, when he was in Mesopotamia, before he dwelt in Charran,
3 And said unto him, Get thee out of thy country, and from thy kindred, and come into the land which I shall shew thee.
4 Then came he out of the land of the Chaldaeans, and dwelt in Charran: and from thence, when his father was dead, he removed him into this land, wherein ye now dwell.
5 And
he gave him none inheritance in it, no, not so much as to set his foot on: yet he promised that he would give it to him for a possession, and to
his seed after him, when as yet he had no child.
6 And God spake on this wise, That his seed should sojourn in a strange land; and that they should bring them into bondage, and entreat them evil four hundred years.
7 And the nation to whom they shall be in bondage will I judge, said God: and after that shall they come forth, and serve me in this place.
Heb 11:13 These
all died in faith, not having received the promises, but having seen them afar off, and were persuaded of them, and embraced them, and confessed that
they were strangers and pilgrims on the earth.
How do you see these things?