Musnad Abu Ya'la al-Mawsili 1:105

107. Khalaf ibn Hisham narrated to us, Abu al-Ahwas narrated to us, from Abu Ishaq, from Ikrimah, who said: Abu Bakr said: I asked the Messenger of Allah, may Allah bless him and grant him peace, "What has caused you to turn gray?" He said: "Hud, al-Waqi'ah, 'Amma Yatasa'alun (an-Naba'), and Idha ash-Shamsu Kuwwirat (at-Takwir) have caused me to turn gray."