مُسْنَدُ أَحْمَدَ
Musnad Ahmad 4271
Musnad of Abdullah bin Mas'ood
It was narrated from Ibn Mas'ood that The Prophet (ﷺ) went to relieve himself and he instructed Ibn Mas'ood to bring him three stones, and he brought two stones and a piece of dung. He threw away the dung and said: “It is impure, bring me a stone.”
Musnad Ahmad 4299A hadeeth saheeh]