This world only knows of Abraham through the Jewish Scriptures. The book quoted in bold above – Genesis – was written around BC 1350 by a descendant of Abraham named Moses. The Jews have preserved this and 38 other books in their national archives.
When Jesus lived on earth (c. AD 0 – AD 33) he taught his followers that all – yes, all – of these ancient books spoke of him. What, then, about the sentences in bold above? Did they (do they) speak about Jesus Christ? Well, yes. Definitely. "And [the LORD] brought [Abram] outside and said, “Look toward heaven, and number the stars, if you are able to number them.” Then [the LORD] said to [Abram], “So shall your offspring be.”
Abram married Sarah but they had no children. When the LORD God promised him children to match the innumerable stars visible in that night sky, Abram believed the LORD. He became a man of faith – a man who walked, in this world, by faith in the LORD God of this world and of the next and of all possible universes and multiverses....
There were two direct consequences of the fact that Abraham believed the LORD. First, Jesus Christ was a descendant of Abraham through Abraham’s son Isaac and grandson Jacob, later renamed Israel. Second, Moses recorded the LORD’s personal blessing for Abraham himself. “And he [Abraham] believed the LORD, and he [the LORD] counted it to him [Abraham] as righteousness.”
Some years later Isaac was born and grew up. As mentioned earlier Abraham was tested. He passed this test of faith at the place now covered by the Dome of the Rock. The LORD God then said this to him. “By myself I have sworn, declares the LORD, because you have done this and have not withheld your son, your only son, I will surely bless you, and I will surely multiply your offspring as the stars of heaven and as the sand that is on the seashore. And … in your offspring shall all the nations of the earth be blessed, because you have obeyed my voice.”
As mentioned earlier also, that “offspring” was Jesus Christ – in whom all nations of the earth have been and are being blessed - even in Jersey - even in AD 2014.
How? Well, the promise to Abraham that his faith was “counted as righteousness” was extended by the LORD Jesus Christ to any, in fact to all who will believe in him and follow him.