It is not haraam to buy and sell after doing the farewell tawaaf, but if the pilgrim does the farewell tawaaf, then stays for what would customarily be regarded as a long time, it is prescribed for him to repeat the tawaaf.
And Allah is the source of strength. May Allaah send blessings and peace upon our Prophet Muhammad and his family and companions. End quote.
Shaykh ‘Abd al-‘Azeez ibn ‘Abd-Allaah ibn Baaz, Shaykh ‘Abd al-Razzaaq al-‘Afeefi, Shaykh ‘Abd-Allaah ibn Qa’ood