Netziv is referring to R. Achai Gaon's derashah on Purim (and his own commentary thereon).
This is the last piece of the She'iltot on Sefer Shemot which is commonly printed without a reference number and instead simply entitled לפורים (although it can also be referred to as She'ilta 67). See e.g. here.
(By the way, the piece of Ha'amek She'elah to which you ...
This is my own interpretation here.
When it says וירא א׳ כי טוב, the statement is naturally attached to something -- what is good? The answer is, the entire context -- the creation is good for the purpose it was made for.
But וירא א׳ את האור כי טוב -- the light was good, regardless of context.
The Ha'amek Davar is explaining two points:
The relevance of "stars"; and
The seeming redundancy of this promise in light of the earlier promise in 13:16.
He explains that the stars represent luminous individuals, and that in light of this there is no redundancy, because the earlier promise of great numbers referred to the people generally, while this ...
I think the Netziv is only supplementing Rashi. Rashi told us that Avraham came to a formerly Semetic land which is now being conquered by a Hammite Canaan, this is somewhat of a contradiction to his prophecy of this land belonging to his Semitic family in the future, so Hashem gave a special reassurance that He will return this land to Avraham's children, ...
There is a name for this. It is called an "asmachta"
Due to some grammatical and theological issues, the statement by the Netziv is misleading as translated.
When he writes: "“there is no tradition that is not hinted at in the biblical text” What he means is the following.
For every oral tradition that was not based on the text of the Torah, there is a ...
There seem to be two expressions of multitude.
One is the comparison to stars. There are very many stars so this is the first expression of multitude.
The second is “if thou be able to count them” which is an additional expression of multitude.
The second expression cannot have the same meaning as the first expression and thus the Haemek Dovor (as is ...