بُلُوغُ الْمَرَامِ
Bulugh al-Maram 276
The Book of Prayer
وَفِي حَدِيثِ أَبِي حُمَيْدٍ , عِنْدَ أَبِي دَاوُدَ : { يَرْفَعُ يَدَيْهِ حَتَّى يُحَاذِيَ بِهِمَا مَنْكِبَيْهِ, ثُمَّ يُكَبِّرَ } [1]
Abu Dawud reported a Hadith narrated by Abu Humaid (RA) to the effect that he [Allah's Messenger (ﷺ)] used to raise his hands and bring them parallel to his shoulders, and then utter the Takbir.
Sunnah.com reference: Book 2, Hadith 156