عَن عمر بن أبي سَلمَة قَالَ: كُنْتُ غُلَامًا فِي حِجْرِ رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ وَكَانَتْ يَدِي تَطِيشُ فِي الصفحة. فَقَالَ لِي رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ «سم الله وكل يَمِينك وكل مِمَّا يليك»

‘Amr b. Umayya told that he saw the Prophet cutting slices from a shoulder of mutton in his hand. He was summoned to prayer, and after throwing it and the knife with which he was slicing it away, he stood up and prayed without performing ablution. (Bukhari and Muslim.)