Sayyiduna Jabir bin Abdullah (may Allah be pleased with them both) said: The Messenger of Allah (peace and blessings be upon him) was delivering the Friday sermon to us when a caravan laden with grain arrived and halted at al-Baqi'. The people went towards that caravan and left the Prophet (peace and blessings be upon him), and only forty men remained with him (peace and blessings be upon him), and I was among them. Allah Almighty then revealed this verse to His Prophet (peace and blessings be upon him): "And when they see some merchandise or amusement, they rush off to it and leave you standing." [Surah al-Jumu'ah: 11]
Note: Forty men are mentioned only through this chain, Ali bin Asim from Husayn; the other students of Husayn contradict him and mention only the number twelve.
The Shaykh said: In the authentic narrations, he (peace and blessings be upon him) was delivering the sermon, and those who mentioned the prayer also meant the sermon by it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجمعة / 5627