What is the linguistic and idiomatic meaning of "al-balāʾ" or "al-ibtilāʾ" (affliction/trial), and what is its purpose?

Linguistically, ibtila (tribulation) means testing. Terminologically, it refers to Allah's testing of His servants with calamities and blessings, for numerous reasons, among them: raising their ranks and expiating sins. "The Prophets are the most severely tested, then those who are most like them, and so on." It also serves to purify the believer and distinguish him from the hypocrite, as stated in His Almighty saying: "And that Allah may purify those who have believed and destroy the disbelievers."