It was narrated from Au Hurairah that the prophet granted a concession allowing estimation for 'Ararya sales, so long as they were five Wasq or less then that (Using translation from Nasāʾī 4541)
أَنَّ النَّبِيَّ ﷺ رَخَّصَ فِي الْعَرَايَا أَنْ تُبَاعَ بِخَرْصِهَا فِي خَمْسَةِ أَوْسُقٍ أَوْ مَا فِي دُونِ خَمْسَةٍ