Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) said that the Messenger of Allah (peace and blessings be upon him) said: "The measure of the people of Makkah and the weight of the people of Madinah are the ones to be relied upon."
Sulayman (al-Tabarani) said: Abu Ahmad narrated it in this way, saying "from Ibn Abbas", and so he differed from Abu Nu'aym in the wording of the hadith; what is correct is what Abu Nu'aym narrated, in both chain and wording.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 11160