Al-Jawhari in al-Sihah says in this regard...
( 8:17 ) All that with which God, to Whom belongs Glory and Majesty, tries His servants is bala’ and ibtila’, whether it is one of the diseases and ailments, or adversities like poverty, humiliation and loss of worldly fortunes, or a thing of an opposite kind such as acquisition of power and glory, wealth, riches, high status, honor, and the like. However, whenever bala’, baliyyah or ibtila’ and the like are mentioned, it is the former kind of things that are meant.
The apology means that in the same way as the earth is the resting place where rainwater comes to rest and abide, the believer is the resting place of sufferings and tribulations, which rush toward him, come to rest in him, and do not depart from him. God willing, we will mention that which is needed for the exposition of this noble tradition in the course of a few sections.
The Meaning Of Trial Let it be known to you that the human souls exist at a level of potentiality from the beginning of their origin, their attachment to the bodies, and their descent to the realm of corporeal existence ( mulk ) , in respect of all things, including knowledge, good and evil traits, and all kinds of perceptive and behavioral faculties. Gradually they move from potentiality to actuality with the grace of God, the Almighty and the Sublime.