It indicates the overcoming of natural scepticism.
There is no plain-vanilla—i.e., pa’al—version of the root a-m-n. In other words, there is no verb le-émon לֶאֱמוֹן. Belief is something that needs to be applied to oneself—the default mode is disbelief. (As they say in Missouri—’Show me.’)
Similarly, there is no verb for ‘going far’: when one simply goes, one holekh—but when one goes far, one marḥiq lekhet—lit. ‘make distance going’.
So when Abraham is persuaded that God will do all that He is promising, he is actively overruling his natural scepticism, to make himself believe.
The verb d-b-r (דבר) is to speak—i.e. it is more formal and intentional. Hence words put in writing are also dbrim* (‘dvarim’); the Ten Commandments in Hebrew are Aseret Hadibrot (The Ten Proclamations); and religious prophets always warned civic leaders to honour at hdbrim awr H’ xivh* etc. (the things that the Lord commanded).
By ‘us’ I’m assuming you mean the Jewish people, and specifically those living in Israel today.
You can’t cherry-pick God’s promises. Even if you accept those verses at face value, the promise is contingent upon the nation remaining faithful to God’s commandments. In the Book of Deuteronomy (chap. 28), God warns Moses:
Actually, no. The Book of Deuteronomy is very explicit on the issue, with the expression avor et-hayarden el-ha’aretz asher Adonai eloheinu noten (‘pass the [River] Jordan to the land which the Lord our God has given’) repeated (in various permutations) a dozen times (2:29 / 3:27 / 4:21, 23, 26 / 9:1 / 11:31 / 12:10 / 27:2,4, 12 / 30:18).
My favourite so far is לֹא אָבָה יַבְּמִי – lo avah yabmi (Deut. 25:9)—meaning ‘He will not perform the duty of my husband’s brother’—which is the official complaint of a childless widow whose brother-in-law refuses to do his fraternal duty of giving her a child after the husband has died.
The expression is unfamiliar because the word yabmi is a conjugation of a curious verb— לִבְּמוֹת libmot — which is awkward to pronounce, not used in other contexts, and even the word for husband’s brother (יבם yavam), is unfamiliar today (in modern Hebrew, it is גיס gis, and can refer to the wife’s brother, as well).
I also love the description of the consequences of such a refusal:
In this chapter of the Song of Songs (or Song of Solomon, as it is sometimes known in English), the woman is describing her lover to her female confidantes. Some of it is rather graphic—but thankfully, the verse you’re asking about is fairly tame:
Coincidentally, that is the subject of a book that I’m writing at the moment.
My favourites are verbal expressions by people that sound startlingly modern, almost colloquial. The following are just a few examples, in my own translation (to convey their vernacular flavour to the ears of native Hebrew speakers):
In our time, for example, we’ve been bandying about the term quantum for decades (e.g. ‘quantum leap’)—although the vast majority of us have only the vaguest idea what that means, and actual quantum devices are only now beginning to appear.
Also, remember that the Israelites had just come out of Egypt, which is one of the few places in the world where they would have encountered iron implements—in construction, in the materiel of the military, etc. Like modern Israel with Soviet materiel in the twentieth century, the ancient Israelites may also have captured iron instruments in battle—they just didn’t know how to produce it, or work it, themselves, until much later.
Last but not least, if indeed, as Jewish tradition has it, Moses himself wrote the Pentateuch, he certainly, as a former Egyptian prince, would have had first-hand knowledge of iron.
But if it’s evidence that the Pentateuch wasn’t written contemporaneously that you want, there’s a much more telling indication…