Hadith: You have said a word which, if mixed with the water of the sea, it would pollute it

عن عائشة رضي الله عنها قالت: قلت للنبي صلى الله عليه وسلم : حَسْبُك من صفية كذا وكذا. قال بعض الرُوَاة: تَعْني قَصِيرة، فقال: «لقد قُلْتِ كلِمَة لو مُزِجَت بماء البحر لَمَزَجَتْهُ!» قالت: وحَكَيْتُ له إِنْسَانًا فقال: «ما أُحِبُّ أَني حَكَيْتُ إِنْسَانًا وإن لي كذا وكذا».
[صحيح] - [رواه أبو داود والترمذي وأحمد]

‘Ā'ishah (may Allah be pleased with her) reported: I said to the Prophet (may Allah's peace and blessings be upon him) "Sufficient for you about Safiyyah is such and such (meaning that she is short)." He said: "You have said a word which, if mixed with the water of the sea, it would pollute it!" She further reported: I once imitated a person before him, so he said: "I do not like that I should imitate a person even in return for such and such."
Sahih/Authentic. - [At-Tirmidhi]

Explanation

‘Ā'ishah (may Allah be pleased with her) mentioned Safiyyah (may Allah be pleased with her) in her absence with what undermines her and offends her; she said that Safiyyah was short to belittle her in the eyes of the Prophet (may Allah's peace and blessings be upon him). Her motive was the usual jealousy among women. Thereupon, the Prophet (may Allah's peace and blessings be upon him) said to her that if her words were mixed with the water of the sea, they would change its color, taste and smell, because of their gravity and extreme danger. She also said: "I imitated a person before him", i.e. ridiculed a person by acting like him. So he (the Prophet) said: I do not like to speak of a person's flaw or imitate him in the way he acts or speaks by way of slighting and belittling him even if I were given such and such of worldly treasures.