From the very first few ayahs of Surah Yaseen, we know that the revelation of the Quran was sent down gradually, according to situation, circumstance, or specific event. It was revealed over approximately 23 years. This was not sent down as a complete, entire volume in one go. It was sent down to complete and end the age of any more revelation. As the guidance is complete, from 23 years of sending down the revelation of the Quran, over a thousand years ago. This revelation is from Almighty Allah the entirely merciful, Allah Subhanahu wa Ta’ala, who wants the best for the creation, so that they can attain salvation.
This guidance is itself mighty and merciful for those who for many generations are in a state of heedlessness, far from guidance, and require warning of the inevitable consequences of eternal reward or eternal punishment for what they live and speak upon the earth, as a result of their own free will, and they are entirely responsible for what they have earned. The mercy and forgiveness is where a person attains the ability to rest in peace. Otherwise, we are not all equal once under the earth in our graves. Some are in punishment, and some are at peace.