Al-Hujuraat - 49:6

يَا أَيُّهَا الَّذِينَ آمَنُوا إِن جَاءكُمْ فَاسِقٌ بِنَبَأٍ فَتَبَيَّنُوا أَن تُصِيبُوا قَوْمًا بِجَهَالَةٍ فَتُصْبِحُوا عَلَى مَا فَعَلْتُمْ نَادِمِينَ
[49:6]
O you who believe! if an evil-doer comes to you with a report, look carefully into it, lest you harm a people in ignorance, then be sorry for what you have done.
O ye who believe! If a wicked person comes to you with any news, ascertain the truth, lest ye harm people unwittingly, and afterwards become full of repentance for what ye have done.
O ye who believe! If an evil-liver bring you tidings, verify it, lest ye smite some folk in ignorance and afterward repent of what ye did.