what does 114.4 : ‘man whispering into heart of another!’ means. How can a man whisper into the heart of another ?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

The interpreters of the Quran discussed the meaning of this verse stating that the whispers are caused by silent talk whose meaning reaches the heart, and this can be done by the devils from among humans as well as the devils from among the jinn; Allaah Says (what means): {…devils from mankind and jinn, inspiring to one another decorative speech in delusion.}[Quran 6:112]

As regards how a human being would inspire whispers into the heart of another human being, then this is done through adorned speech and by showing advice.

Tafseer Fat’h Al-Qadeer reads: “As regards the devil from among the jinn, he inspires whispers in the heart of the human beings. As regards the devil from among the humans, then his inspiring whispers in the heart of the human beings means that he shows himself as the compassionate adviser and so he affects the heart of the human being through his words which he says as if he were giving him a piece of advice the same way the devil affects it with his whispers.”

Allaah Knows best.