In Genesis 22, God blessed Abraham saying he would have a great number of descendants through whom all nations on earth would be blessed.

What did Abraham do to receive so great a blessing?

He was willing to sacrifice his son as a burnt offering to God

And said, By myself have I sworn, saith the LORD, for because thou hast done this thing, and hast not withheld thy son, thine only son:

That in blessing I will bless thee, and in multiplying I will multiply thy seed as the stars of the heaven, and as the sand which is upon the sea shore; and thy seed shall possess the gate of his enemies;

And in thy seed shall all the nations of the earth be blessed; because thou hast obeyed my voice. Genesis 22:16-18