The Messenger of Allah ﷺ said, and Qutayba reported it as something traced back to the Prophet ﷺ, "Do not engage in najsh."
حدثنا قتيبة وأحمد بن منيع قالا حدثنا سفيان عن الزهري عن سعيد بن المسيب
قال رسول الله ﷺ وقال قتيبة يبلغ به النبي ﷺ قال لا تناجشوا
No references are available.
Bukhari transmitted it in the Book of Sales, chapter "A man should not sell over the sale of his brother, nor make an offer over the offer of his brother, until the first gives permission or withdraws," Hadith 2140, from the narration of Sufyan bin Uyayna, by the same chain. Muslim also narrated it, Hadith 1515, from the narration of Abu Hurairah.There are also narrations on this subject from Ibn Umar [Bukhari, Hadith 2162, and Muslim, Hadith 1516] and Anas [Bayhaqi 5/319, and Abu Yaala 5/155, Hadith 2767].