Chasidut su Isaia 55:10

Deuteronomy 29:9: It appears to me to say the following about this verse: it says earlier in the Torah [in the previous chapter] that "...until this day, Hashem did not give you a heart to know, ear to hear, eye to see" [Deuteronomy 29:3]. [This means that] the entire service of Moshe Rabbeinu was for the Jewish people to hear all mitzvot from his mouth; his intent was to imbue their hearts with the power of holiness of Hashem with his holy words. The Shechina would speak from his throat, and the goal was that the Jewish people would not be able to transgress anything in the Torah. It says in the Torah, "just like snow comes from heaven and never returns... so, too, My words will not return empty-handed [Isaiah 55:10]. This was the level that Moshe spoke [to Hashem], and Hashem answered him [directly] with a voice and He wanted to place a holiness within him so that [listening to Moshe's words would] be equal to hearing them from Hashem. This is the meaning of the previous verse, "Hashem did not give you a heart to know...": The Jewish people were lifted up to a very lofty level after 4o years [of being in the desert], and it says "...on this day, you've become a people for G-d" [Deuteronomy 27:9]. [This means that] at the end [of the Jewish people's journey], when Moshe Rabbainu would speak, the experience was that of Mount Sinai (--of G-d speaking--) and thus the Torah would never be removed from their mouth. This is also explains the verse: "I heard the voice of my G-d and did according to all that was commanded me" [Deuteronomy 26:14]. "I heard to voice..." means that I did what G-d commanded and I'm listening now just like I did at Mount Sinai; I did all that I'm commanded and I haven't missed anything. [Moses] successfully elevated you so that you can stand before Hashem without any separation. Moshe Rabbainu expresses this covenant with everyone, not just the generation of the desert [Deuteronomy 29:14]. In the future of the generation, the tzaddik of the generation will also be speaking. This is [literally as if] Moshe Rabbainu [is speaking to you], which, [in turn, is as if] you're hearing it from G-d. As it says in the original verse, all will stand before G-d [meaning] in every future generation through the tzaddik.

Deuteronomy 11,21 “In order that your days and the ‎days of your children will be numerous on the soil as long as ‎there is a heaven above the earth.” We find a verse in ‎Isaiah 55,10 where the prophet expresses a similar sentiment, ‎paraphrasing Moses’ words here. Instead of speaking of heaven ‎and earth, the prophet Isaiah uses the parable of snow and rain as ‎phenomena that are enduring in our world, adding that as long as ‎these phenomena will be beneficial on earth, so long will G’d’s ‎word be effective on earth and benefit mankind as a ‎whole.