It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both): A boy from Banu Hashim and I came riding a donkey and passed in front of the Messenger of Allah (peace and blessings be upon him) while he (peace and blessings be upon him) was praying, and he did not break off his prayer because of that. Two little girls of Banu Abd al-Muttalib came and took hold of the knees of the Messenger of Allah (peace and blessings be upon him), and he (peace and blessings be upon him) made peace between them and separated them, but he did not break off his prayer because of that.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3504