Abu Hurairah (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings of Allah be upon him) said: "Do not practice Najsh (artificially inflating prices)." Imam Tirmidhi says:
1- The hadith of Abu Hurairah (may Allah be pleased with him) is Hasan Sahih,
2- In this chapter, ahadith have also been narrated from Ibn Umar and Anas (may Allah be pleased with them),
3- And some people of knowledge have acted upon this; they have declared «نجش» to be impermissible,
4- «نجش» is that a person who can distinguish between good and bad goods comes to the seller and bids a price higher than the actual price, and this happens when a buyer is present, and the only purpose is that the buyer is deceived by this, and the one who bids the price has no intention of buying, but only wants the buyer to be deceived by his bidding. This is a kind of deception,
5- Shafi'i says: If a person does «نجش» , then because of this action, the one who does «نجش» will be sinful, but the sale will be valid, because the seller is not doing «نجش» .