If one asks, "If the Paradise that Adam was thrown out of was in heaven, as the majority of the scholars assert, then is it possible for Iblis to enter Paradise, although he was expelled from it by Allah's decision (when he refused to prostrate before Adam)''
Basically, the response to this would be that the Paradise which Adam was in, was in the heavens, not on the earth, as we explained in the beginning of our book Al-Bidayah wan-Nihayah.
The majority of scholars said that Shaytan was originally prohibited from entering Paradise, but there were times when he sneaked into it in secret. For instance, the Tawrah stated that Iblis hid inside the snake's mouth and entered Paradise. Some scholars said that it is possible that Shaytan led Adam and Hawwa' astray on his way out of Paradise. Some scholars said that he led Adam and Hawwa' astray when he was on earth, while they were still in heaven, as stated by Az-Zamakhshari. Al-Qurtubi mentioned several beneficial Hadiths here about snakes and the ruling on killing them.
﴿فَتَلَقَّى ءَادَمُ مِن رَّبِّهِ كَلِمَاتٍ فَتَابَ عَلَيْهِ إِنَّهُ هُوَ التَّوَّابُ الرَّحِيمُ ﴾
(37. Then Adam received from his Lord Words. And his Lord pardoned him (accepted his repentance). Verily, He is the One Who forgives (accepts repentance), the Most Merciful.)