SURAH AL-BAQARAH
Ayah 9.
يُخَادِعُونَ اللّهَ وَالَّذِينَ آمَنُوا وَمَا يَخْدَعُونَ إِلاَّ أَنفُسَهُم وَمَا يَشْعُرُونَ
They seek to deceive Allah and those who believe, but they deceive none but themselves, though they are not aware.
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Their “act” to deceive the believers in accepting them so that they can destroy the religion from within. However they deceive none but themselves, though they are not aware.
Allah says that they are the ones that are deceived by their own intention and actions (as they will find out later in the hereafter).
Example like a dog who is on a 50 metres lease (a very long lease). The dog is able to run around freely within the length of the lease. The dog barks at people intimidating the people around it. The dog thinks that he is in control. If the dog runs around hard and when he reached the 50th metre he will be yanked back as hard as he had ran. It is not aware at first that it is on a lease (as the lease is very long). In the end the dog gets a painful yank. Only now it is aware that it is on a rope.
The same goes to the Munafiquun who finally get to be aware when they receive the punishment as described in the next ayah. In this world, they are not aware that they are deceiving themselves just like the dog who was deceived by the long leash, while the people around already knew.