Paul quoted several of Isaiah’s prophecies to help explain that no one can work their way to heaven. The secret is to trust God:
Romans 9:30-33 Even though the Gentiles were not trying to follow God’s standards, they were made right with God. And it was by faith that this took place. But the people of Israel, who tried so hard to get right with God by keeping the law, never succeeded. Why not? Because they were trying to get right with God by keeping the law instead of by trusting in him. They stumbled over the great rock in their path.
The great rock is Jesus:
God warned them of this in the Scriptures when he said,
‘I am placing a stone in Jerusalem that makes people stumble,
a rock that makes them fall.
But anyone who trusts in him
will never be disgraced.’
The scriptures Paul referred to are in Isaiah 8 (calling Israel and Judah to trust God) and Isaiah 28 (warning of judgement on a wayward Israel and Judah if they didn’t change their ways very soon).