Al-Bayhaqī (6/31) likewise narrated it through two chains from Sufyān, from Ḥanzalah, from Ṭāwūs, from Ibn ʿUmar—raised all the way to the Prophet.

I say: The chain is sound, just as Ibn al-Mulaqqin stated in al-Khilāṣah (pp. 64–65). Ibn Ḥibbān, al-Dāraquṭnī, al-Nawawī, Ibn Daqīq al-ʿĪd and al-ʿAlāʾī also declared it authentic, as cited in Fayd al-Qadīr. Some transmitters, however, reported it from Sufyān with the wording “from Ibn ʿAbbās” in place of “Ibn ʿUmar,” and that is a mistake which I clarified while documenting the ḥadiths of sales for the Juristic Encyclopaedia and again in Irwāʾ (no. 1331).

Imām Abū Jaʿfar al-Ṭaḥāwī—may Allah have mercy on him—said:

“We reflected on this ḥadith and found that Mecca possessed neither fruit nor cultivation at that time, nor had it in the ages before. Do you not see Abraham’s words, peace be upon him: ‘Our Lord, I have settled some of my progeny in a valley without vegetation’ (Q 14:37)? Mecca was simply a trading town; pilgrims would arrive with their merchandise and sell it there. Medina, by contrast, was the land of date-palms, and its people lived on its produce. Alms-taxes were brought into it, and whatever levy was due there was taken by volume measure. Hence the Prophet ﷺ made all other cities follow the standards of these two blessed cities.

People needed weight measures for the prices of what they bought, and for other transactions involving commodities, the payment of zakāt, and so forth—handing over in return goods that they themselves measured by volume. The Sunnah had prohibited concluding a salam (advance-purchase) contract of a weighed commodity for another weighed commodity, and likewise of a measured-by-volume commodity for another of its kind; but it allowed a salam of a measured item for a weighed one, and of a weighed item for a measured one. It also forbade selling a weighed commodity for another weighed commodity except weight for equal weight, and selling a measured commodity for another measured commodity except measure for equal measure. In all of this, the standard of weight is that which prevailed in Mecca, and the standard of volume measure is that of the people of Medina; these are not to be altered. Even if people depart from them to their opposites, they must still refer, with respect to goods governed by volume, to what the people of volume measures adhered to on that day, and, with respect to goods governed by weight—"