Prophet (SAW)'s Prayers  When buying or selling at the Market

Recite:

بِسْمِ اللَّهِ إِنِّي أَسْأَلُكَ خَيْرُ هَذِهِ السُّوقِ وَخَيْرُ مَا فِيهَا وَأَعُوذُ بِكَ مِنْ شَرِّهَا وَشَرِّ مَا فِيهَا اللَّهُمَّ إِنِّي أَعُوذُ بِكَ أَنْ أُصِيبَ فِيهَا يَمِينَاً فَاجِرَةً أَوْ صَفْقَةً خَاسِرَةً

"I entered in the name of Allah, I seek refuge in You (Allah) for the good in the bazaar and for the good of what is in it (the bazaar). O Allah, I seek refuge in you from false oaths and deception in transaction". (Hisnul Hasin)

Additionally:

On returning from the bazaar, recite any ten ayats of the Qur'an (i.e. from anywhere) (Hisnul Hasin from Tabarani)