A man came to Muhammad bin Ka'b (may Allah have mercy on him) and said: "We find these words in some books, that there are some servants of Allah, whose tongues are sweeter than honey, but their hearts are harder than patience. They show gentleness to people as if they are wearing the skin of a sheep, but they cunningly seek the world through religion." Allah, the Mighty and Majestic, says: "Do they dare against Me? And do they deceive Me? By My honor! I will impose upon them such a trial that even the wise will be left astonished and bewildered." Muhammad bin Ka'b (may Allah have mercy on him) said: "This matter is present in the Book of Allah," and then he recited this verse: ﴿وَمِنَالنَّاسِمَنْيُعْجِبُكَقَوْلُهُفِيالْحَيَاةِالدُّنْيَاوَيُشْهِدُاللَّهَعَلَىمَافِيقَلْبِهِوَهُوَأَلَدُّالْخِصَامِ﴾ (And among the people is he whose speech pleases you in worldly life, and he calls Allah to witness as to what is in his heart, yet he is the fiercest of opponents). The man said: "We know about whom this verse was revealed." Muhammad bin Ka'b (may Allah have mercy on him) said: "The ruling is first revealed about one person, but then it becomes general for everyone."
Hadith Referenceسنن سعید بن منصور / كتاب التفسير / 361