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