“I, Yahweh, have spoken it. It will come about and I will do it. I will not go back, neither will I spare, neither will I repent. According to your ways, and according to your doings, will they judge you, says the Lord Yahweh.”
God added His seal to what was to happen. Now nothing could prevent it for He had determined it. He had spoken, and so it would come about (Isaiah 55:11). He stressed that this time there would be no alteration in His purpose. He would not go back to how things were before, or withdraw from His purpose, He would not spare, He would not have a change of mind. He would act towards them exactly as they deserved. They would receive what their behaviour merited.
The same warning comes to us all. God is gracious and longsuffering, but if we continue in disobeying Him and rejecting His commandments, His patience will come to an end. And then there can be only judgment.