The Prophet ﷺ forbade najsh.
أخبرنا قتيبة عن مالك عن نافع
أن النبي ﷺ نهى عن النجش
No references are available.
Sourcing, Bukhari reported it in the Book of Tricks, chapter on what is disliked regarding outbidding, hadith 6963, from Qutayba. Muslim reported it in the Book of Transactions, chapter on the prohibition of a man selling over his brother's sale and bidding over his bid, and so on, hadith 1516, from the hadith of Malik through this chain. It is also in the Muwatta (Yahya's version) 2/684, and in the Kubra, hadith 6091.