And God blessed them. And God said to them, “Be fruitful and multiply and fill the earth and subdue it, and have dominion over the fish of the sea and over the birds of the heavens and over every living thing that moves on the earth.”  And God said, “Behold, I have given you every plant yielding seed that is on the face of all the earth, and every tree with seed in its fruit. You shall have them for food.  And to every beast of the earth and to every bird of the heavens and to everything that creeps on the earth, everything that has the breath of life, I have given every green plant for food.” And it was so.  And God saw everything that he had made, and behold, it was very good. And there was evening and there was morning, the sixth day.
Occasionally I get hung up on words. Bless is one such word. What does it really mean? Is it more than just a superstitious response to a sneeze? Is it more than the end of a worship service? Etymology doesn’t help too much:
Bless: Old English bletsian, bledsian, Northumbrian bloedsian "to consecrate, make holy, give thanks," from Proto-Germanic *blodison "hallow with blood, mark with blood," from *blotham "blood" (see blood (n.)). Originally a blood sprinkling on pagan altars. This word was chosen in Old English bibles to translate Latin benedicere and Greek eulogein, both of which have a ground sense of "to speak well of, to praise," but were used in Scripture to translate Hebrew brk "to bend (the knee), worship, praise, invoke blessings." L.R. Palmer ("The Latin Language") writes, "There is nothing surprising in the semantic development of a word denoting originally a special ritual act into the more generalized meanings to 'sacrifice,' 'worship,' 'bless,'" and compares Latin immolare (see immolate). Meaning shifted in late Old English toward "pronounce or make happy," by resemblance to unrelated bliss. No cognates in other languages. Related: Blessed; blessing.
Blessing (n.) Old English bletsunga, bledsunge; see bless. Meaning "gift from God" is from mid-14c. In sense of "religious invocation before a meal" it is recorded from 1738. Phrase blessing in disguise is recorded from 1746.
blessed (adj.) late 12c., "supremely happy," also "consecrated" (c. 1200), past participle adjective from bless (v.). Reversed or ironic sense of "cursed, damned" is recorded from 1806. Related: Blessedly; blessedness.
Ultimately, the idea in English is related to the Hebrew in functionality, but it has a loaded background involving sacrifice and religious ritual. The Hebrew has a bigger meaning.
Barak means literally to kneel, to bless, or… to curse. It can describe the act of worship. It can be a greeting. And, in this instance, it is something God does. He blesses. When we bless someone or something, we are hoping to confer divine favor. The religious aspect of the concept is something we get after sin, once sacrifice becomes necessary. But the idea of blessing connects to God without all of the religious trappings. When God blesses, the divine favor is assured because we are not requesting or hoping the blessing will be fulfilled, He is favoring of His own accord.
Here, the blessing is followed by and probably related to two commands. Humanity is to multiply and fill the Earth. (As the birds and fish were blessed with this idea of multiplication on day 5, we can see this blessing/command applying to the animals from day 6 as well.) However, mankind is also to exercise dominion over the other creatures. Both of these ideas have been corrupted with sin. Sex is a good thing designed by God, but sin has completely polluted and confused the issue. Likewise, dominion is understood as a negative because of the abuse of creation we see today, but as intended it was all about stewardship and care. We were not to Lord over creation, but to manage it as God intended. We were supposed to be a blessing in creation.
Bonhoeffer latches onto the fact that Barak can mean both blessing and curse, and speaks about how the blessings God conferred on humanity here did indeed become curses in the Fall. We will see more about that later.