Al-Imam Ali (p.b.u.h), said:

Hadith n. 471

471. Amir al-mu’minin, peace be upon him, said: There is no good in silence over matters involving wisdom just as there is no good in speaking with ignorance.

Hadith n. 472

472. Amir al-mu’minin, peace be upon him, said in his prayer for seeking rain: O My God, send us rain by submissive clouds not by unruly ones.

As-Sayyid ar-Radi says: This is an expression of wonderful eloquence, because Amir al-mu’minin, peace be upon him, has likened the cloud which is accompanied by thunder, lighting, wind and flashes with unruly camels who throw away their saddles and throw down their riders, and likened the clouds free from these terrible things to the submissive camels which are easy to milk and obedient to ride.

Hadith n. 473

473. It was said to Amir al-mu’minin, peace be upon him, : We wish you had changed your grey hair, O Amir al-Mu’minin. Then he said: Dye is a way of adornment while we are in a state of grief.

As-Sayyid ar-Radi says: Amir al-mu’minin, peace be upon him, is referring to the death of the Messenger of Allah, peace be upon him and his descendants.

Source: https://www.al-islam.org/nahjul-balagha-part-2-letters-and-sayings