In one narration these words are additional, and al-Tabarani also recorded it in al-Mu'jam al-Kabir: The Prophet (peace and blessings be upon him) used to say: "Do not meet the traders until they reach the market, and do not sell for the bedouins, even if he is the brother of one of you, or his father, or his mother." The narrators of Ahmad are the narrators of the Sahih.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب البيوع / 6366