Why did Allah create pain and cause His prophets to suffer it?

Pains, whether physical or psychological, were created by Allah for profound wisdoms, among them: expiation of sins, elevation of ranks, and increase of good deeds. The Prophet (peace be upon him) said: "No fatigue, nor disease, nor sorrow, nor sadness, nor hurt, nor distress befalls a Muslim, even if it were a prick of a thorn, but Allah expiates some of his sins thereby." Rather, the prophets, who are the most severely tested of people, are afflicted with pain, and this does not contradict the status of prophethood.