Silsilat al-Ahadith al-Sahihah

It is narrated from Sayyiduna Anas (may Allah be pleased with him) that the Messenger of Allah (peace and blessings of Allah be upon him) said: "When Allah, the Blessed and Exalted, fashioned the form (structure) of Adam (peace be upon him), He left him as he was. Iblis began to walk around him and observe him. When he saw that he was hollow from within (i.e., empty inside), he said: 'I will succeed over him, for he is a creature who will not be able to control himself.'"