Sahih Al Bukhari Hadith Number 739

Narrated Nafi`: Whenever Ibn `Umar started the prayer with Takbir, he used to raise his hands: whenever he bowed, he used to raise his hands (before bowing) and also used to raise his hands on saying, “Sami`a l-lahu liman hamidah”, and he used to do the same on rising from the second rak`a (for the 3rd rak`a). Ibn `Umar said: “The Prophet (peace be upon him) used to do the same.”

10  Call to Prayers (Adhaan)
Hadith number 739
Volume no 1
Chapter: 86 (To raise one’s hands after finishing the second Rak’a (on standing for the third Rak’a)