Muwatta Imam Malik Book of Business Transactions, Hadith 96
Yahya related to me from Malik from Nafi from Abdullah ibn Umar that the Messenger of Allah ﷺ said, "Do not let any of you bid against each other."
حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنْ نَافِعٍ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ، أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ " لاَ يَبِعْ بَعْضُكُمْ عَلَى بَيْعِ بَعْضٍ " .