Moses declared that promise fulfilled in Deut. 1:10.
Consider further that in Deuteronomy 28, where God gives Israel a conditional curse that if they would not obey Him, He would destroy them. Specifically look at Deut. 28:62 where God promises to reverse the blessing making them few in number whereas they were numbered as the stars of heaven.
Then in Deut. 31:28 Moses says - "Gather unto me all the elders of your tribes, and your officers, that I may speak these words in their ears, and call heaven and earth to record against them."
And finally Moses says in Deut. 32:1 - "Give ear, O ye heavens, and I will speak; and hear, O earth, the words of my mouth" as he begins to speak to the Israelites. In Joshua 24:22, Joshua calls the Israelites to be witnesses against themselves to hold to this same promise.
Then take all of these allusions, especially the last couple of verses above, and compare them with Isaiah 1:1-2, 10:
And it becomes a bit clearer that when heaven and earth are referred to figuratively in scripture they are referring to leaders and the people they rule, specifically the leaders of Israel and her people.
This above is not entirely conclusive for many, but again I'm just laying foundation here. Next we'll look through the books of history and see what they have to say.
In Truth and Love.