Dr. Tal`at Muhammad `Afifi, Dean of the Faculty of Da`wah at Al-Azhar University, states: “Looking into what has been mentioned in the Qur’an about the way Iblis approached Adam (peace and blessings be upon him) we find out that it was through waswasah, or whispering and insinuation. Referring to this, Allah Almighty says: “But Satan whispered evil to him: he said, ‘O Adam! shall I lead thee to the Tree of Eternity and to a kingdom that never decays?’” (Taha: 120)
Waswasah does not necessarily mean that Iblis changed to another creature, as it runs through people like blood.”
Shedding more light on the issue, Sheikh `Atiyyah Saqr, former head of Al-Azhar Fatwa Committee adds:
“Allah Almighty says: “Then Satan whispered to them that he might manifest unto them that which was hidden from them of their shame, and he said: Your Lord forbade you from this tree only lest ye should become angels or become of the immortals. And he swore unto them (saying): Lo! I am a sincere adviser unto you.” (Al-A`raf: 20-21)
It is clear from the aforementioned verse that Iblis talked with both Adam and Eve after its expulsion from Paradise. Allah Almighty referred to that talk as waswasah.
The question now is: How did such waswasah take place despite that Iblis was not actually in Paradise with Adam and Eve?
The apparent meaning of the verse refers to the fact that the dialogue between the two parties took place in an ordinary form. The talk was not in the form of soliloquie vibrating in hearts of both; verbal talk itself is sometimes called waswasah, especially when it is done secretly.
What I want to say here is that there has been much ado about this very issue, and there is no authentic Hadith that provides a clear-cut response.
We can not rule out that Iblis talked to Adam and Eve while he was standing by the gate of Paradise, with Adam and Eve inside. With this possibility, it is clear that Iblis did not gain any entry to the Paradise after its expulsion.
Finally, some people claim that Iblis managed to enter Paradise by hiding in the belly of a beautiful snake, and that makes a snake one of the animals mostly hated by humans. Undoubtedly, the above claim has no legal backing.”