“God knows the person whom He is testing and is confident that the outcome will be for the good.
As a certain Midrash teaches: just as the potter knocks on the newly completed vessel to ascertain if it is sound, so does God knock on a man.
A potter will refrain from knocking on an obviously cracked vessel, it would only break.
He tests the pots that are whole”
--Rabbi Adin Steinsaltz
From The Candle of God, p. 204 by Rabbi Adin Steinsaltz
