"The Messenger of Allah went to the toilet and said: 'Bring me three stones.' So I brought him two stones and a piece of dung. He took the two stones and threw the dung away, saying: 'It is impure.'" (Using translation from Ibn Mājah 314)
أَنَّ رَسُولَ اللهِ ﷺ أَتَى الْخَلَاءَ وَقَالَ ائْتِنِي بِثَلَاثَةِ أَحْجَارٍ فَالْتَمَسْتُ فَوَجَدْتُ حَجَرَيْنِ وَلَمْ أَجِدِ الثَّالِثَ فَأَتَيْتُهُ بِحَجَرَيْنِ وَرَوْثَةٍ فَأَخَذَ الْحَجَرَيْنِ وَأَلْقَى الرَّوْثَةَ وَقَالَ إِنَّهَا رِكْسٌ