Why does Allah Almighty send the Dajjal to Earth? Is it to test our faith or for another reason?

Life, with its good and evil, is a trial and a test from Allah the Almighty for His servants. Allah the Almighty said: "He who created death and life to test you [as to] which of you is best in deed," and He said: "And We test you with evil and with good as a trial; and to Us you will be returned." The emergence of the Dajjal is one of the greatest trials, and the Prophet, peace and blessings be upon him, sought refuge from him in his prayer. So, the wisdom behind the emergence of the Dajjal is to test the faith of the servants.