3 “You have proved and visited Mine heart in the night-season”. For this Mine heart has been proved by the visitation of tribulation. “You have examined Me by fire, and iniquity has not been found in Me.” Now not night only, in that it is wont to disturb, but fire also, in that it burns, is this tribulation to be called; whereby when I was examined I was found righteous.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)