It was narrated that Ibn 'Abbas said: "When the Prophet (ﷺ) came to Al-Madinah, they were the worst people in weights and measures. Then Allah, Glorious is He revealed: "Woe to the Mutaffifun (those who give less in measure and weight)",[1] and they were fair in weights and measures after that.
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا عَبْدُ الرَّحْمَنِ بْنُ بِشْرِ بْنِ الْحَكَمِ، وَمُحَمَّدُ بْنُ عَقِيلِ بْنِ خُوَيْلِدٍ، قَالاَ حَدَّثَنَا عَلِيُّ بْنُ الْحُسَيْنِ بْنِ وَاقِدٍ، حَدَّثَنِي أَبِي، حَدَّثَنِي يَزِيدُ النَّحْوِيُّ، أَنَّ عِكْرِمَةَ، حَدَّثَهُ عَنِ ابْنِ عَبَّاسٍ، قَالَ لَمَّا قَدِمَ النَّبِيُّ ـ صلى الله عليه وسلم ـ الْمَدِينَةَ كَانُوا مِنْ أَخْبَثِ النَّاسِ كَيْلاً فَأَنْزَلَ اللَّهُ سُبْحَانَهُ {وَيْلٌ لِلْمُطَفِّفِينَ} فَأَحْسَنُوا الْكَيْلَ بَعْدَ ذَلِكَ .
sunnah.com