Sunan an-Nasa'i, Volume 5, Book 44, Hadith 4509 (DarusSalam) ⓘ
It was narrated from Ibn 'Umar that: the Prophet forbade artificially inflating prices.
أَخْبَرَنَا قُتَيْبَةُ، عَنْ مَالِكٍ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، أَنَّ النَّبِيَّ صلى الله عليه وسلم نَهَى عَنِ النَّجْشِ .
also referenced under: Hadith 4505 (Reference) & Book 44, Hadith 57 (In-Book)