The Prophet ﷺ said, "None of you should sell over the sale of his brother."
أخبرنا قتيبة بن سعيد عن مالك والليث واللفظ له عن نافع
عن النبي ﷺ أنه قال لا يبيع أحدكم على بيع أخيه
Bukhari narrated it in the Book of Sales, Chapter "A man should not sell over the sale of his brother, nor make an offer over the offer of his brother, until he gives permission or leaves it," hadith no. 2139, and Muslim in the Book of Sales, Chapter on the prohibition of a man selling over the sale of his brother, etc., hadith no. 1412, after hadith no. 1514, from the hadith of Malik through this same route, and it is in the Muwatta (Yahya's recension) 2/683, and in Al-Kubra, hadith no. 6094.