"The Messenger of Allah said to me: 'Fast one day and you will have the reward of ten.' I said: 'Let me fast more.' He said: 'Fast two days and you will have the reward of nine.' I said: 'Let me fast more than that.' He said: 'Fast three days and you will have the reward of eight." (One of the narrators) Thabit said: "I mentioned that to Mutarrif and he said: 'I only see that he is making more effort for less reward.'"

لِي رَسُولُ اللَّهِ ﷺ صُمْ يَوْمًا وَلَكَ أَجْرُ عَشْرَةٍ فَقُلْتُ زِدْنِي فَقَالَ صُمْ يَوْمَيْنِ وَلَكَ أَجْرُ تِسْعَةٍ قُلْتُ زِدْنِي قَالَ صُمْ ثَلاَثَةَ أَيَّامٍ وَلَكَ أَجْرُ ثَمَانِيَةٍ قَالَ ثَابِتٌ فَذَكَرْتُ ذَلِكَ لِمُطَرِّفٍ فَقَالَ مَا أُرَاهُ إِلاَّ يَزْدَادُ فِي الْعَمَلِ وَيَنْقُصُ مِنَ الأَجْرِ وَاللَّفْظُ لِمُحَمَّدٍ

[Machine] The Prophet ﷺ said to him, "Fast for one day and you will be rewarded for ten days." He said, "Increase for me, O Messenger of Allah, for I have the ability." He said, "Fast for two days and you will be rewarded for nine days." He said, "Increase for me, for I find strength." He said, "Fast for three days and you will be rewarded for eight days."

أَنَّ النَّبِيَّ ﷺ قَالَ لَهُ صُمْ يَوْمًا وَلَكَ عَشَرَةُ أَيَّامٍ قَالَ زِدْنِي يَا رَسُولَ اللهِ إِنَّ بِي قُوَّةً قَالَ صُمْ يَوْمَيْنِ وَلَكَ تِسْعَةُ أَيَّامٍ قَالَ زِدْنِي فَإِنِّي أَجِدُ قُوَّةً قَالَ صُمْ ثَلَاثَةَ أَيَّامٍ وَلَكَ ثَمَانِيَةُ أَيَّامٍ

[Machine] The Messenger of Allah ﷺ said to him, "Fast for one day and you will have the reward of ten days." He said, "Increase me, O Messenger of Allah." He said, "Fast for two days and you will have the reward of nine days." He said, "Increase me." He said, "Fast for three days and you will have the reward of eight days." Thabit said, "So I informed Muattib ibn Abdullah about that, and he said, 'I do not see anything except that it increases in action and decreases in reward.'" Abu Abdullah added, "Some of them increased upon others."

إِنَّ رَسُولَ اللهِ ﷺ قَالَ لَهُ «صُمْ يَوْمًا وَلَكَ أَجْرُ عَشَرَةِ أَيَّامٍ» قَالَ قُلْتُ زِدْنِي يَا رَسُولَ اللهِ قَالَ «صُمْ يَوْمَيْنِ وَلَكَ تِسْعَةٌ» قَالَ قُلْتُ زِدْنِي قَالَ «صُمْ ثَلَاثَةَ أَيَّامٍ وَلَكَ أَجْرُ ثَمَانِيَةِ أَيَّامٍ» قَالَ ثَابِتٌ فَأَخْبَرْتُ بِذَلِكَ مُطَرِّفَ بْنَ عَبْدِ اللهِ فَقَالَ مَا أُرَاهُ إِلَّا يَزْدَادُ فِي الْعَمَلِ وَيَنْقُصُ مِنَ الْأَجْرِ قَالَ أَبُو عَبْدِ الرَّحْمَنِ زَادَ بَعْضُهُمْ عَلَى بَعْضٍ

"عَنِ ابْن عَمْرٍو: أَنَّ رَسُولَ اللهِ ﷺ قَالَ: صُمْ يَوْمًا وَلَكَ عَشْرَةُ أَيَّامٍ، قَالَ: زِدْنِى يَارَسُولَ الله! قَالَ: صُمْ يَوْمَيْنِ وَلَكَ تِسْعَةُ أيَّامٍ، قَالَ: زِدْنى يَا رَسُولَ الله! قَالَ: صمْ ثَلاَثةَ أَيَّامٍ وَلَكَ ثَمَانيَةُ أيَّامٍ".