Radak: This is the continued existence of a matter unconditionally. Even though it says "Nishba Hashem" in third person, it says "Eten" (first person) like I explained above (refer to 62:6:5:1*).
2.
Malbim: Hashem bound Himself [that He must fulfill it].
2)
Why does it mention "Yemino" and "Zero'a Uzo"?
1.
Radak: He has the ability to preserve Shalom, and their enemies will not rule over them again. The matter is repeated in different words, for the right hand is the strong hand in man, and so Kel speaks in a metaphor
1
.
2.
Malbim: Yemino is miraculous conduct done via deeds of Tzadikim and Yisrael's merit. Zero'a is miraculous conduct via Himself, not via [man's] merit or deeds. If Yisrael merit, He will do with Yemino. If not, He will do with "Zero'a Uzo", like it says above "Livshi Oz Zero'a Hashem", "va'Tosha Lo Zero'o" (51:9, 59:16) like I explained above (refer to 59:16:4:3, 59:16:5:3). Chazal said (Brachos 6a) that Yemino is Torah, i.e. if they will merit and guard His Torah. If they will not merit, it will be bi'Zro'a Uzo - via the power of Tefilin, i.e. the promise of Yisrael's greatness written in Parashas Tefilin.
Why is this a mere metaphor? Do we not infer from "b'Tzelem Elokim Asah Es ha'Adam" (Bereishis 1:27) that if man's Yamin is stronger than his Smol, it is because Hashem's Midah of Yamin is stronger than His Midah of Smol?! (PF)
3)
Why does it say "Im Eten Es Deganech Od"?
1.
Malbim: Until now, nearby enemies dwelled in their land and ate their grain. This will no longer be.
4)
Why does it discuss Bnei Nechar drinking their wine?
1.
Malbim: Bnei Nechar are far away. They did not dwell in their land and eat their grain. However, they drank their wine, which they sent afar for trade
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. This will no longer be.
