It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "Jibril (peace be upon him) commanded me to say the takbir," or he (peace and blessings be upon him) said: "that you should put the takbir first."
No one narrated this hadith from Nafi' (may Allah have mercy on him) except Usamah (may Allah have mercy on him), and Ibn al-Mubarak (may Allah have mercy on him) is alone in narrating it.
Hadith Referenceالمعجم الأوسط / باب الباء / 3218
Hadith Takhrij«أخرجه البخاري فى «صحيحه» برقم: 246، ومسلم فى «صحيحه» برقم: 2271، 3003، والبيهقي فى «السنن الكبرى» برقم: 172، والبزار فى «مسنده» برقم: 5986، 5987»