The Prophet ﷺ forbade intercepting goods before they reached the markets, forbade inflating prices through false bidding, and said, "None of you should sell over the sale of another."When he was traveling in haste, he would combine the Maghrib and Isha prayers.
حدثنا عبد الرحمن حدثنا مالك عن نافع
أن النبي ﷺ نهى عن تلقي السلع حتى يهبط بها الأسواق ونهى عن النجش وقال لا يبع بعضكم على بيع بعض وكان إذا عجل به السير جمع بين المغرب والعشاء
Its chain of transmission is sahih. It is, in reality, four hadiths combined: the prohibition against intercepting merchandise (before it reaches the market), the prohibition against najsh, the prohibition against one person outbidding another in a sale, and combining two prayers. I did not find the first one in Muwatta, but the other three are found in it at 2:170, 171 and 1:161. However, Muhammad bin Hasan narrated the first and second together in his Muwatta from Malik, 335-336, and the meaning of the last one has already appeared at 4472. See also what preceded in the Musnad of Ibn Abbas, 2313, 3482, and in the Musnad of Ibn Masud, 4096, and see Muntaqa, 2840, 2843, 2844.As for najsh, with a fatha on the noon and a sakin on the jeem, Ibn Athir said, it means that a man praises merchandise in order to promote it and make it desirable, or raises its price, while he himself has no intention of buying it, so that someone else falls for it. The origin of the term comes from driving wild game from one place to another.