The Midrash (BaMidbar Rabbah 16) quotes R’ Acha haGadol’s derush on the pasuk “Yaveish chatzir naveil tzitz u’dvar Elokeinu yakum l’olam,” (Yeshayahu 40:8):
למה הדבר דומה? למלך, שהיה לו אוהב והתנה עמו ואמר לו: לך עמי ואני נותן לך מתנה. הלך עמו ומת. אמר המלך לבנו של אוהבו: אעפ"י שמת אביך, איני חוזר בי במתנה שאמרתי לו, בוא וטול אתה! כך הדבר, המלך, מלך מלכי המלכים הקב"ה. והאוהב זה אברהם, שנאמר (שם מא): זרע אברהם אוהבי. אמר לו הקדוש ברוך הוא: בא לך עמי (בראשית יב): לך לך מארצך וממולדתך ומבית אביך. התנה עמו, שיתן לו מתנה, שנאמר (שם יג): קום התהלך בארץ. וכן הוא אומר (שם): כי כל הארץ אשר אתה רואה לך אתננה. אמר לו הקב"ה למשה: אעפ"י שהתנתי עם האבות ליתן להם את הארץ ומתו, איני חוזר בי,
The Midrash reassures us that we still have a claim on Eretz Yisrael despite the fact that it was promised originally to Avraham and he is long dead. Why this affirmation now? Avraham Avinu had been dead already for hundreds of years by the time Bnei Yisrael left Egypt, ostensibly with the goal of settling Eretz Yisrael. Furthermore, wasn’t the land originally promised to Avraham in trust for his descendents, not as a personal gift – what is the hava amina that Hashem should not deliver?
The answer (as explained by the Shem m’Shmuel) is that there is little bit of Avraham Avinu that lives on inside each and every one of us. Avraham Avinu thus theoretically had the ability to personally collect on the promise of Eretz Yisrael through us.
The tragedy of the meraglim was that Bnei Yisrael disassociated themselves from this legacy of the Avos and their love of the land. That little piece of Avraham within was no longer alive, it no longer had meaning to the generation of the midbar. That ability of Avraham to personally collect was lost.
What right then did we have to the land? The Midrash answers that Hashem’s promise is irrevocable -- even if we fail to live up to the model of the Avos, Eretz Yisrael is ours.
I think this Midrash more generally addresses the inevitable rift that emerges between generations. Not only Avraham Avinu, but the spirit of all fathers and grandfathers eventually dies off, as children go their own way and pursue their own dreams and destiny. Does that mean that ideas and values are lost? Does that mean that the promises made to and by our forefathers have no meaning? Not necessarily. The dor hamidbar was not a dor of Avraham Avinu’s, but Hashem nonetheless was willing (and I don’t think the Midrash means begrudgingly) to reaffirm his promise of Eretz Yisrael. Despite there being differences between our generation and that of our parents or grandparents, and our generation and that of our children, there is a sense of continuity to yahadus which cannot be extinguished.