What is the definition of denial and how does it occur?

Rejecting evil means changing it, and it is one of the obligatory duties and rituals of Islam. Quranic texts and prophetic traditions have affirmed this, such as the Almighty's saying: "And let there be [arising] from you a nation inviting to [all that is] good, enjoining what is right and forbidding what is wrong, and those will be the successful," and the Prophet, peace and blessings be upon him, said: "Whoever among you sees an evil, let him change it with his hand; if he cannot, then with his tongue; if he cannot, then with his heart—and that is the weakest of faith." This hadith clarifies the levels of change, such that verbal denunciation is not sufficient for one who is able to use his hand, nor is heart-felt disapproval sufficient for one who is able to use his tongue.