"لَوْ أَنَّ اللهَ -تَعَالى- عَذَّبَ أَهْل السَّمَاءِ والأرْضِ، عَذبهُمْ غَيرَ ظَالِم، وَلَوْ أَدْخَلَهُم فِي رَحْمَتِه كانَتْ رَحْمَتُهُ أَوْسَع مِن ذُنُوبهم، وَلَكِنَّهُ كمَا قَضَى يُعَذِّبُ من يَشَاءُ، وَيرْحَمُ مَن يَشَاءُ، فَمَنْ عَذَّبَ فَهُوَ الحَقُّ، وَمَنْ رَحِمَ فَهُوَ الحَقُّ، وَلَوْ كانَ ذَلِكَ مِثْلَ أحُدٍ ذَهَبًا تُنْفِقُهُ في سَبِيلِ اللهِ مَا قُبِلَ مِنْكَ حَتَّى تُؤْمِنَ بِالقَدَرِ كُلِّهِ، خَيرِهِ وَشَرِّه".
I went to Ubayy b. Ka’b and said him : I am confused about Divine decree, so tell me something by means of which Allah may remove the confusion from my mind. He replied : were Allah to punish everyone in the heavens and in the earth. He would do so without being unjust to them, and were he to show mercy to them his mercy would be much better than their actions merited. Were you to spend in support of Allah’s cause an amount of gold equivalent to Uhud, Allah would not accept it from you till you believed in divine decree and knew that what has come to you could not miss you and that what has missed you could not come to you. Were you to die believing anything else you would enter Hell. He said : I then went to ‘Abd Allah b. MAs’ud and he said something to the same effect. I next went to Hudhaifah b. al-Yaman and he said something to the same effect. I next went to Zaid b. Thabit who told me something from the Prophet (May peace be upon him) to the same effect. (Using translation from Abū Dāʾūd 4699)
فقَالَ «إِنَّ اللَّهَ لَوْ عَذَّبَ أَهْلَ سَمَاوَاتِهِ وَأَهْلَ أَرْضِهِ عَذَّبَهُمْ غَيْرَ ظَالِمٍ لَهُمْ وَلَوْ رَحِمَهُمْ كَانَتْ رَحْمَتُهُ خَيْرًا لَهُمْ مِنْ أَعْمَالِهِمْ وَلَوْ أَنْفَقْتَ مِثْلَ أُحُدٍ فِي سَبِيلِ اللَّهِ مَا قَبِلَهُ اللَّهُ مِنْكَ حَتَّى تُؤْمِنَ بِالْقَدَرِ وَتَعْلَمَ أَنَّ مَا أَصَابَكَ لَمْ يَكُنْ لِيُخْطِئَكَ وَأَنَّ مَا أَخْطَأَكَ لَمْ يَكُنْ لِيُصِيبَكَ وَلَوْ مُتَّ عَلَى غَيْرِ هَذَا لَدَخَلْتَ النَّارَ»
[Machine] I have debated with the people of destiny until they embarrassed me. Do you have any knowledge to inform me? They said, "If Allah punished the people of the heavens and the earth, He would punish them without being unjust. And if He admitted them into His mercy, His mercy would be greater than their sins. But as He has decreed, He punishes whom He wills and has mercy on whom He wills. So whoever is punished, it is true, and whoever is shown mercy, it is true. And even if you were to spend the equivalent of Uhud mountain in the cause of Allah, it would not be accepted from you until you believe in the entirety of destiny, its good and bad." Then 'Imran said to Abu al-Aswad when he narrated the Hadith, "I heard that from the Messenger of Allah ﷺ, and Abdullah and Ubayy bin Ka'b heard it with me." So Abu al-Aswad asked them to narrate it to him from the Messenger of Allah ﷺ.
إِنِّي قَدْ خَاصَمْتُ أَهْلَ الْقَدَرِ حَتَّى أَحْرَجُونِي فَهَلْ عِنْدَكُمْ عَلِمٌ فَتُحَدِّثُونِي؟ فَقَالُوا «لَوْ أَنَّ اللهَ ﷻ عَذَّبَ أَهْلَ السَّمَاءِ وَالْأَرْضِ عَذَّبَهُمْ غَيْرُ ظَالِمٍ وَلَوْ أَدْخَلَهُمْ فِي رَحْمَتِهِ كَانَتْ رَحْمَتُهُ أَوْسَعَ مِنْ ذُنُوبِهِمْ وَلَكِنَّهُ كَمَا قَضَى يُعَذِّبُ مَنْ يَشَاءُ وَيَرْحَمُ مَنْ يَشَاءُ فَمَنْ عُذِّبَ فَهُوَ الْحَقُّ وَمَنْ رُحِمَ فَهُوَ الْحَقُّ وَلَوْ كَانَ لَكَ مِثْلُ أُحُدٍ تُنْفِقُهُ فِي سَبِيلِ اللهِ مَا قَبِلَ مِنْكَ حَتَّى تُؤْمِنَ بِالْقَدَرِ كُلِّهِ خَيْرِهِ وَشَرِّهِ» ثُمَّ قَالَ عِمْرَانُ لِأَبِي الْأَسْوَدِ حِينَ حَدَّثَهُ الْحَدِيثَ «سَمِعْتُ ذَلِكَ مِنْ رَسُولِ اللهِ ﷺ وَسَمِعَهُ مَعِي عَبْدُ اللهِ وَأُبَيُّ بْنُ كَعْبٍ» فَسَأَلَهُمَا أَبُو الْأَسْوَدِ فَحَدَّثَاهُ عَنْ رَسُولِ اللهِ ﷺ
"لَوْ أَنَّ اللهَ عَذَّبَ أَهْلَ سَمَاوَاتِهِ وَأهْلَ أَرْضه لَعَذبهُمْ وَهُوَ غَيرُ ظَالِمٍ لَهُمْ، وَلَوْ رَحِمَهُمْ لَكَانَتْ رَحْمَتُهُ لَهُمْ خَيرًا مِنْ أَعْمَالهم، وَلَوْ أنَفَقْتَ مِثْلَ أُحُد ذَهبًا فِي سَبِيلِ الله ما قَبِلَهُ الله مِنْكَ حَتَّى تُؤْمِن بِالقَدَرِ فَتَعْلَمَ أَنَّ مَا أَصَابَكَ لَمْ يَكُنْ لِيُخْطئَكَ وَمَا أَخْطَأكَ لَمْ يَكُنْ لَيُصِيبَكَ، وَلَوْ مُتَّ عَلَى غَير هَذَا لَدَخَلتَ النَّارَ".