Hawzah News Agency – The merciful prophet of Islam, peace be upon him and his household says:

أدنَى الكفرِ أنْ يَسمعَ الرّجُلُ مِن أخيهِ الكَلِمَةَ فيَحْفَظَها علَيهِ يُريدُ أنْ يَفْضَحَهُ بها، اُولئكَ لا خَلاقَ لَهُم.

'The most basic level of infidelity is for a man to hear a fellow brother say something and memorize it for future to use against him in order to shame him with it. Those are worthless people indeed.'

Source: Bihar al-Anwar, v. 77, p. 193, no. 11