3 I have declared the former things from the beginning; and they went forth out of my mouth, and I shewed them; I did them suddenly, and they came to pass.
4 Because I knew that thou art obstinate, and thy neck is an iron sinew, and thy brow brass;
5 I have even from the beginning declared it to thee; before it came to pass I shewed it thee: lest thou shouldest say, Mine idol hath done them, and my graven image, and my molten image, hath commanded them.
God is omniscient. All-knowing. He is the only One Who tells the future and Who is right 100% of the time. He points out that He reminds Israel of His omniscience because He knows how stubborn and rebellious they are.
The reason He reminds them that He has told them what will happen long before it happens, and that His track record is perfect, is that He knows they would give credit to their images and idols instead of to Him.
Lest we be smug and arrogant, thinking we would never be as sinful as the nation of Israel has been, we need to look at, say, the abortion rate in America; or the number of fatherless homes; or the number of teens doing drugs, alcohol and sex, just for starters. Then we could talk about the murder rates in our big cities, especially in Chicago. And then we can fall to our knees and beg God to deliver us, because we are not able to deliver ourselves.