Section: Trading in the mosque
185. Prayers for the person who trades in the mosque
Narrated Abu Hurairah: That the Messenger of Allah (ﷺ) said: "When you see someone selling or buying in the Masjid then say:
لَا أَرْبَحَ اللَّهُ تِجَارَتَكَ
لَا اَرْبَحَ اللّٰهُ تِجَارَتَكَ
laa arba'ha Allahu tijaarataka
Translation
May Allah not profit your business.
This is because the mosques were not built for this purpose.
ReferenceSahih (Albani). Tirmidhi: 1321