The Ramban understood the following verse as the Biblical source for the mitzvah to settle and build up the Land of Israel:
"You shall take possession of the Land and settle it; for I have given you the Land to possess it" (Num. 33:53)
The following remarkable story was told by Yigal Gal-Ezer, who served as the vice state comptroller of Israel. In his younger days, Gal-Ezer would often visit Rav Kook in order to be inspired from his holy presence.
The Yemenite Visitor
During one visit, I found the rabbi immersed in a complex Talmudic topic. Suddenly, there was a hesitant knocking at the door. The door opened partially, and a Yemenite Jew - slight of stature, with streaks of white in his beard and peiyot - entered the room.
The guest locked the door behind him and stood in the doorway, his back to the door. He lowered his head to the floor, as if he was afraid to look at the rabbi directly.
Rav Kook lifted his eyes from his Talmud and studied the man.
"Come closer, my son." With a pleasant voice, the Rav tried to instill confidence in the visitor.
With slow steps, the man drew near to the rabbi's desk. He remained standing, head down.
"What is disturbing you, my son?"
"Honored rabbi," he began with a frail, hesitant voice. "I came to ask the rabbi an important question."
"Ask, my son, ask," Rav Kook responded, encouraging him to continue.
"For twenty-five years, I have worked from morning to evening, backbreaking work. I weeded land so that orchards could be planted. I planted saplings, I dug up stones from fields, I excavated foundations for houses in Eretz Yisrael. I invested my strength and days in hard labor. But I barely earn enough to support my family.
"I would like to ask: is it permissible for me to emigrate to America? Perhaps there my fortune will shine and I will be able to properly support my family."
The Yemenite worker finished speaking, and remained standing in silence.
For several minutes, Rav Kook sat, deep in thought. Abruptly, the rabbi stood up, pointed to his chair and commanded the man, "Sit."
The guest shook with trepidation. "Honored rabbi," he stammered, "it is improper that a stranger should sit on your chair."
"Sit," the rabbi repeated.
With short, hesitant steps, he walked around the desk until he came to the rabbi's chair. Nervously, he sat down.
As soon as he sat, his head dropped to the desk and he fell into a deep sleep. A short while later, he woke up, startled and disoriented.
The Heavenly Court
"What happened when you slept?" asked the Rav.
"I dreamt that I had passed on to the next world. My soul ascended to heaven. When I reached heaven's gates, there was an angel standing at the entrance who directed me to the heavenly court. There I saw scales - scales of justice.
Suddenly carriages drawn by horses swung out in front of me. They were loaded with packages, some small, some medium-sized, and some large. The angels began unloading the packages, and they placed them on one side of the scales. It sunk down due to the weight of the load, until it nearly reached the ground.
'What is the meaning of these packages?' I asked the angel standing before me.
'These are your sins and faults, mortal man, from your days on earth. Everything is accounted for.'
I felt broken and disheartened.
Suddenly, other carriages arrived. These were loaded with dirt, rocks, stones, and sand. The angels loaded all of these on the other side of the scales. It began to lift up the side of sins and transgressions.
'What is the meaning of these bundles of dirt?' I asked.
'These are the stones, rocks, and dirt which your hands labored to remove from the ground of the Holy Land. They come to speak in your defense, for your share in settling the Land of Israel...'
Trembling, I stared at the scale's side of merits. I saw it dipping lower and lower, lifting the side of guilt. Then the side of merits ceased moving; it stopped just as it outweighed the sins by a small amount."
"You see, my son," Rav Kook told the man gently. "You have received your answer from heaven."
(Adapted from Malachim Kivnei Adam, pp. 321-322 sent to Arutz Sheva by Rabbi Chanan Morrison RavKookTorah.org)