After the devastation of the flood, humanity steps out into an empty and desolate world. The survivors are in desperate need of a deep renewal of life. God grants them a foundational blessing that reaffirms their existence and purpose, establishing them as the new fathers of the human family.
The primary approach among commentators is that this blessing is almost identical to the one given to the first man at the dawn of creation. However, a renewal was necessary. Because the floodwaters had returned the earth to a state of chaos, the world was now experiencing a rebirth [רד״ק]. Furthermore, since God had destroyed the vast majority of humanity, the original blessing appeared to be canceled. It had to be officially reaffirmed to guarantee the continuation of life [ביאור שטיינזלץ, קאסוטו]. This renewal serves as a message to Noah: just as a remnant of life survived through his merit, he and his sons will become the fathers of all future generations [ביאור יש״ר].
The divine communication was directed at both Noah and his sons. While it is possible that the sons received this message through their father, another view suggests that the sons themselves achieved a state of prophecy, allowing them to hear the words directly from God [רד״ק].
When stepping out of the ark and seeing the sheer emptiness of the world, Noah was gripped by anxiety over the fact that only four men remained on earth. The divine words were meant to calm this fear, promising the eventual growth of a large human society [מלבי״ם]. At this stage, the encouragement to multiply is not yet a practical duty, but rather a pure divine blessing. God is granting them the actual physical strength and capability to bring children into the world; the formal command to do so only appears later [העמק דבר, רש ר הירש].
Beyond physical reproduction, populating the world carries a deep spiritual meaning. Since large portions of the earth are not suitable for human settlement, this expansion cannot be strictly geographical. The physical earth is naturally lacking, and humanity is tasked with filling it with spiritual perfection. By doing good deeds, humans draw down the divine presence, repairing the spiritual emptiness left behind by the sins of the flood generation [אלשיך].
A notable difference between this moment and the original blessing given to the first man is the absence of any mandate to conquer the earth or rule over the animals. This change reflects a shift in the relationship between humans and nature. The once harmonious connection has been severed, replaced by a dynamic of distance and fear. Consequently, humanity's primary task is no longer to control the outside world, but to focus on internal and moral growth [רש ר הירש]. Conversely, another perspective views this omission as proof of Noah's elevated spiritual status. While the first man was closer to an animalistic state and therefore had to actively struggle and conquer nature, Noah achieved such a high level of spiritual perfection that the animal kingdom naturally submitted to him out of awe, making any forceful conquest completely unnecessary [מלבי״ם].