Al-An'am: 112
"And thus We have made for every prophet an enemy..."
Just as We have placed a barrier between you and your enemies, so too did We act with the prophets before you and their enemies. We did not prevent them from showing enmity, for it contains a trial that serves as the cause for the manifestation of steadfastness and patience, and the increase of reward and recompense.
"...devils..."
The word shayatin (devils) is in the accusative case (nasb) as a substitute (badal) for "enemy," or it is treated as a double object, similar to the verse: "And they attributed to Allah partners—the jinn" (Al-An'am: 100).
"...inspiring to one another..."
The devils of the jinn whisper to the devils of mankind. Likewise, some jinn inspire others, and some humans inspire others. Malik ibn Dinar said: "The human devil is more severe upon me than the jinn devil; for when I seek refuge in Allah, the jinn devil departs from me, whereas the human devil comes to me and drags me into disobedience openly."
"...decorative speech..."
That is, what they adorn of speech, whispering, and incitement to sin, while disguising it.
"...in deception."
Meaning: trickery and catching one off guard.
"But had your Lord willed, they would not have done it."
They would not have done that—meaning they would not have shown you enmity, nor would they have inspired one another with decorative speech—had He restrained them and not left them to their own devices.
"So leave them and that which they invent. And [it is] so the hearts of those who do not believe in the Hereafter will incline toward it and that they will be satisfied with it and that they will commit that which they are committing."