It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that he said: "While we were walking with the Messenger of Allah (peace and blessings be upon him), he (peace and blessings be upon him) passed by some children who were playing, and among them was a boy. It was as if that displeased the Messenger of Allah (peace and blessings be upon him). He (peace and blessings be upon him) said to him: 'Do you bear witness that I am the Messenger of Allah?' He replied: 'Do you bear witness that I am the Messenger of Allah?' He (peace and blessings be upon him) said: 'Be gone! You will never go beyond your rank.' Sayyiduna Umar (may Allah be pleased with him) said: 'O Messenger of Allah, let me strike off his head.' He (peace and blessings be upon him) said: 'O Umar, if he is the one (the Dajjal) you fear, you will never be able to kill him.'"
Hadith Referenceالمعجم الأوسط / باب الألف / 1161
Hadith Takhrij«أخرجه مسلم فى «صحيحه» برقم: 2924، وابن حبان فى «صحيحه» برقم: 6783، وأحمد فى «مسنده» برقم: 3680، 4457، وأبو يعلى فى «مسنده» برقم: 5172، 5223، والبزار فى «مسنده» برقم: 1688، 1689، وابن أبي شيبة فى «مصنفه» برقم: 38685، والطحاوي فى «شرح مشكل الآثار» برقم: 2946»