Ubaidullah bin 'Amr bin Abi Walid عبيد الله بن عمرو بن أبي الوليد · Wages (Kitab Al-Ijarah)

The Messenger of Allah (ﷺ) as saying: None of you must buy in opposition to one another ; and do not go out to meet the merchandise, (but one must wait) till it is brought down to the market.