In the Holy Qur'an

Allah commands you that when you judge between people you judge with justice (4:58)

In the Traditions

Imam Jafar said, "The proof of the man of intellect lies in two things: truthful words and correct actions. The man of intellect does not say something which the intellect rejects, neither does he expose himself to suspicion, nor abandon the help of those who have been tested. Knowledge guides him in his actions; gnosis is his certainty in the paths he treads, and forbearance is his companion at all times."