Imagine if I told my ten-year-old daughter, "I guarantee that one of your descendants will do something amazing like cure cancer, which will make him a famous hero in every country in the world." What are the odds that prediction would come true?
I don't know the exact odds, of course, but they would be infinitesimal!
Abraham was told something very similar to that (three times) in Genesis 18:18, 22:18, and 26:4 when God said, "In your offspring all the nations of the earth shall be blessed."
Think about this for a few minutes. The prophecies made to Abraham were written down in around 1400 BC by Moses. Even if the most radical liberal skeptics are right (which they're not) and the Torah wasn't compiled until the 6th Century BC, that's still over 500 years before Jesus was born, and 2500 years before our time, when he has become a blessing to people from every nation in the world, just like the prophecy said.
The other promises in the same narrative, like Abraham would have a son and he would become a great nation, had already taken place by the time they were written down, so the writer could have simply "reverse engineered" those prophecies and made up the idea that they were predicted long before. But the prophecy that "all the nations shall be blessed" had hardly been fulfilled at that time, by any stretch of the imagination. So no matter how you slice it, the claim that "in your offspring all the nations of the earth shall be blessed" was a wild one, which would have been inconceivable and even delusional unless it had been made by an all-powerful God with the ability to make it come to pass.
And what God did do, just as he said he would, is akin to the prediction I mentioned at the beginning above. In fact, it's more like me saying to my daughter, "One of your descendants will become famous on 30 planets," because at the time the promise to Abraham was written down, the writer only knew about the few nations that surrounded him. He himself couldn't have known that Jesus would become a blessing to hundreds of nations that didn't even exist at the time! But God knew all that--he planned it out and made it happen.
When I shared this with some friends recently, one said, "I wonder if there were other similar prophecies made in the ancient near east," as if that might cast doubt on the spectacular nature of this one. I had never heard of such, but just in case I checked online and searched a collection of ancient near eastern prophecies on Google Books. I couldn't find any similar prophecy. But even if some exist, none of them came true like the one given to Abraham!
(Also--and this is something missed by the skeptics who find parallels to biblical stories etc in other ancient literature--Satan often copycats biblical truth when he creates other religions, and he has enough supernatural ability and knowledge to do that even prior to God's revelation being recorded. So just because an idea may have existed before it was written down by God's people doesn't mean it was necessarily an inspiration or source for the biblical account.)
God is real and the Bible is true, and while there are many other evidences for those truth claims, none are more compelling than fulfilled prophecy, because only God can know the future and predict it in detail long before it comes to pass. A mathematician named Peter Stoner once studied eight fulfilled prophecies from the Old Testament and concluded that the chances of them coming true by chance was 1 in 1017 or 1 in 100,000,000,000,000,000. That’s one in one hundred quadrillion!
Stoner didn't even include the amazing prophecy given to Abraham that "in your offspring all the nations of the earth shall be blessed." Imagine what the odds would be if he had, and take some time to enjoy the blessing that Jesus Christ can bring to your life by reading or listening to the Bible.