Is criticizing colleagues' professional performance considered backbiting, and is informing the manager about a colleague's mistakes at work considered tale-bearing, especially given that the nature of the work requires evaluating colleagues' performance?

It is not permissible to seek out a Muslim's shortcomings and spread them, because of the Almighty's saying: "And do not spy, nor backbite one another," and the Prophet, peace and blessings be upon him, said: "For whoever seeks out the shortcomings of his Muslim brother, Allah will seek out his shortcomings." If what is said is a lie, then it is slander. However, if a Muslim sees a shortcoming or error in his brothers, he must advise them.

If a Muslim is asked about a person for the purpose of dealing with them, it is permissible for him to mention a shortcoming or error related only to the work, and it is not permissible to mention other defects unrelated to the matter. He must state the full truth in employee evaluations without delving into errors unrelated to the work.