Hadithcore
Hadith #2109800

Muslim has:

"A Muslim must not offer a price above that offered by another Muslim."

وَلِمُسْلِمٍ: { لَا يَسُمِ اَلْمُسْلِمُ عَلَى سَوْمِ اَلْمُسْلِمِ } [1]‏ .‏

References2 variants
Sunnah.com reference
Book 7, Hadith 35
Arabic/English book reference
Book 7, Hadith 0