QUL

"And O Adam! Dwell you and your wife in Paradise, and eat thereof as you both wish, but approach not this tree otherwise you both will be of the wrongdoers (19)Then Shaytan whispered suggestions to them both in order to uncover that which was hidden from them of their private parts (before); he said: "Your Lord did not forbid you this tree save you should become angels or become of the immortals. (20)And he 'Qāsamahuma': "Verily, I am one of the sincere well-wishers for you both. (21)

Allah states that He allowed Adam and his wife to dwell in Paradise and to eat from all of its fruits, except one tree. We have already discussed this in Surat Al-Baqarah. Thus, Shaytan envied them and plotted deceitfully, whispering and suggesting treachery. He wished to rid them of the various favors and nice clothes that they were enjoying.

وَقَالَ

(He (Shaytan) said) uttering lies and falsehood,

مَا نَهَاكُمَا رَبُّكُمَا عَنْ هَٰذِهِ الشَّجَرَةِ إِلَّا أَن تَكُونَا مَلَكَيْنِ

("Your Lord did not forbid you this tree save you should become angels...") meaning, so that you do not become angels or dwell here for eternity. Surely, if you eat from this tree, you will attain both, he said. In another Ayah,

قَالَ يَا آدَمُ هَلْ أَدُلُّكَ عَلَىٰ شَجَرَةِ الْخُلْدِ وَمُلْكٍ لَّا يَبْلَىٰ

(Shaytan whispered to him, saying: "O Adam! Shall I lead you to the Tree of Eternity and to a kingdom that will never waste away?")[20:120]. Here, the wording is similar, so it means, 'so that you do not become angels' as in;

يُبَيِّنُ اللَّهُ لَكُمْ أَن تَضِلُّوا

((Thus) does Allah make clear to you (His Law) lest you go astray.)[4:176] meaning, so that you do not go astray, and,

وَأَلْقَىٰ فِي الْأَرْضِ رَوَاسِيَ أَن تَمِيدَ بِكُمْ

(And He has affixed into the earth mountains standing firm, lest it should shake with you;)[16:15] that is, so that the earth does not shake with you.

وَقَاسَمَهُمَا 

(And he 'Qāsamahuma'), swore to them both by Allah, saying,

إِنِّي لَكُمَا لَمِنَ النَّاصِحِينَ

("Verily, I am one of the sincere well-wishers for you both.") for I was here before you and thus have better knowledge of this place.

It is a fact that the believer in Allah might sometimes become the victim of deceit. Qatadah commented on this Ayah, "Shaytan swore by Allah, saying, 'I was created before you, and I have better knowledge than you. Therefore, follow me and I will direct you.'"