לרפואת בתי היראה עדינה בת שבע בת נעכא גיטל בתוך שח"י
This world conceals far more than it reveals. We see a physical Universe which conceals the spirit of Hashem which gives life to everything in existence. Part of the mourning over the exile involves internalizing how much we are missing when we only perceive the physicality of the world. The pasuk says that when Moshiach comes וראו כל בשר יחדיו כי פי ה' דיבר - All flesh will see together that the mouth of Hashem speaks. This doesn't mean that something NEW will be created when Moshiach but that what was part of creation all along will be revealed for all to see [see Tanya Ch. 36-37]. Every "thing'" דבר – is מדבר speaks, its Divine source. We just can't see it at this time.
The gemara says [Rosh Hashana 31a] says that the world will exist 6000 years and be destroyed for 1000 years. This means that first the world was בכח - potential. Then it was actualized – בפועל, into a physical world for 6000 years, just as first we have Shabbos [בכח] followed by six days [בפועל]. After the 6000 years the world will be elevated to the state of בכח - meaning, it will be revealed how EVERYTHING emerges from its Divine source which is a "destruction" in our conceptualization, because we perceive reality as the physical matter in front of our eyes. At that time we will see והיה ה' למלך על כל הארץ ביום ההוא יהיה השם אחד ושמו אחד – Hashem will be recognized as King and automatically ונשגב ה' לבדו ביום ההוא – Hashem will reign alone on that day. When we see everything as אלוקות – the original forms as we perceive them are destroyed. We will live in a world where it will be evident that אז ירננו כל עצי היער – All of nature sings to Hashem.
[עפ"י ספרי הפנימיות]