Musnad Ahmad 30:1209

Wahb ibn Jarir narrated to us, my father narrated to us, he said: I heard Yunus, from al-Zuhri, from Sa'id ibn al-Musayyib and Abu Salamah, from Abu Hurayrah, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "We are more entitled to doubt than Ibrahim, when he said: 'My Lord, show me how You give life to the dead. He said: Do you not believe? He said: Yes, but [I ask] so that my heart may be at rest' [Al-Baqarah: 260]."