It is narrated from Salim (may Allah have mercy on him) that Ibn Umar (may Allah be pleased with them both) used to say that when the Messenger of Allah (peace and blessings be upon him) stood for the prayer, he would raise his hands until they were level with his shoulders, then he would say the takbir. (This hadith has passed in detail.)
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2313