وَلَا تَكَلَّمْ بِكَلَامٍ تَعْتَذِرُ مِنْهُ غَدًا
Do not say words for which you would need to apologize tomorrow.
Angry insults, unverified allegations, and disclosure of secrets can cause lasting harm. The advice asks a person to consider consequences before speaking.
It does not mean that someone who makes a mistake must refuse to apologize. Apology and repair are essential after wrongdoing. Prevention, however, is better than careless speech.
The same principle applies before forwarding an accusatory message.