"Messenger of Allah went out to relieve himself. So he said: 'Bring me tree stones.'" He said, "So I came with two stones and a piece of dung. So he took the two stones, and left the dung. He said: 'It is Riks (a degenerative or filthy thing)."  

خَرَجَ النَّبِيُّ ﷺ لِحَاجَتِهِ فَقَالَ الْتَمِسْ لِي ثَلاَثَةَ أَحْجَارٍ قَالَ فَأَتَيْتُهُ بِحَجَرَيْنِ وَرَوْثَةٍ فَأَخَذَ الْحَجَرَيْنِ وَأَلْقَى الرَّوْثَةَ وَقَالَ إِنَّهَا رِكْسٌ