The Women - 4:45
Allah knows your enemies better. Allah is sufficient as a friend and owner, and Allah is sufficient as a helper.
The hypocrites, who appear to be friends but are in fact enemies, and whom the believers are not aware of, are implied.
The Repentance/9:101
Some of the Arabs, both from among you and from the people of the city, are hypocrites. They have become arrogant in hypocrisy. You do not know them, but We know them. We will punish them with a double torment and then they will be punished with a great torment.
The Hypocrites/63:1
"When the hypocrites come to you, they say, "We bear witness that you are the messenger of Allah. Allah knows that you are His messenger, and Allah testifies that the hypocrites lie."
The Hypocrites/63:2
They take their oaths as a shield and lead astray from the way of Allah. How evil is what they do.
The Hypocrites/63:3
Because they disbelieved after they believed, so their hearts were sealed; they do not understand.
The Hypocrites/63:4
When you see them, you like their appearance. If they speak, you listen to their words. They are like stumps that stand upright. They think every noise is against them; they are the real enemies; beware of them. May Allah curse them; how they turn away!