Sahih Bukhari Volume 6, Book 60, Hadith Number 61.

Narrated By Abu Huraira : Allah’s Apostle said, “We have more right to be in doubt than Abraham when he said, ‘My Lord! Show me how You give life to the dead.’ He said, ‘Do you not believe?’ He said, ‘Yes (I believe) but to be stronger in Faith.'” (2.260)