The future redemption of Jerusalem and the land of Israel is painted with the profound imagery of a wedding. Instead of the bleak reality of destruction and exile, there is a complete renewal of the three-way bond between the people, the land, and God.
The initial focus is on the relationship between the people and their land. The imagery of taking a bride speaks to ownership, acquisition, and settlement. The Israelites will return to acquire the land, develop it, and settle there permanently and united [רש״י, מצודת דוד, שד״ל וביאור שטיינזלץ]. This serves as a metaphor for the restoration of Israel's sovereignty and kingship [אבן עזרא]. Because Jerusalem is often personified in the Bible as a woman, it is natural to use the picture of a groom happily bringing his bride under his care to describe the joy of the returning citizens taking hold of their city [שד״ל].
The specific comparison of a young man marrying a young woman carries deep meaning about the nature of this reunion. Primarily, it highlights the perfect, natural fit between the Israelites and their homeland. When foreign nations ruled the land, the pairing was inappropriate and unnatural, much like an older man marrying a young woman. The return of Israel to its land, however, is the most beautiful and natural match [רד״ק, צאינה וראינה]. Furthermore, this connection emphasizes a feeling of absolute renewal and a clean slate. The return will not feel like a man remarrying his divorced wife, an arrangement often weighed down by past baggage and incomplete affection. Instead, the bond will be as fresh and whole as if the land had never been destroyed and the people never exiled [מלבי״ם]. From another perspective, just as a groom is completely absorbed in his wedding day and freed from other obligations, the Israelites in the future will be entirely immersed in their spiritual connection [אהבת יהונתן].
The focus then shifts to God's relationship with Jerusalem, characterized by the overwhelming excitement and joy of a groom on his wedding day [מצודת דוד]. God will rejoice in His people with the fresh, renewing joy of a couple beginning their life together [רד״ק וביאור שטיינזלץ]. This celebration will be public and open, marked by the creation of a new covenant that completely washes away the memory of past troubles [מלבי״ם]. Reaching this moment, however, requires a process of preparation. Just as a bride observes a period of counting and purification before dressing in white and stepping under the wedding canopy, the Israelites endure the pains of exile to cleanse and correct themselves. Only after this process do they achieve the ultimate spiritual connection, where God rejoices over them just as a groom rejoices over his bride [אהבת יהונתן].