Musnad Ahmad 27:1536

Harun ibn Ma'ruf narrated to us, Abdullah ibn Wahb narrated to us, 'Amr ibn al-Harith informed me that 'Abd al-Rahman ibn al-Qasim narrated to him, from his father, from 'Abdullah ibn 'Umar, from the Messenger of Allah (may Allah bless him and grant him peace) that he said: "Indeed, the sun and the moon do not eclipse for the death of anyone, nor for his life. But they are two signs from the signs of Allah. So when you see them, then pray."