ENOfficial
Ibn 'Umar said: "The Prophet (Allah bless him and give him peace) summoned a cupper, so he cupped him. Then he asked him: “How much is your tax?” He said: “Three measures of grain,” so he reduced his tax by one measure and gave him his fee.”
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا هَارُونُ بْنُ إِسْحَاقَ، قَالَ: حَدَّثَنَا عَبْدَةُ، عَنِ ابْنِ أَبِي لَيْلَى، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، أَنَّ النَّبِيَّ صلى الله عليه وسلم، دَعَا حَجَّامًا فَحَجَمَهُ وَسَأَلَهُ: كَمْ خَرَاجُكَ؟ فَقَالَ: ثَلاثَةُ آصُعٍ، فَوَضَعَ عَنْهُ صَاعًا وَأَعْطَاهُ أَجْرَهُ.
sunnah.com