known - by thine own observation and reading of Scripture.
heard - from tradition of the fathers.
everlasting, etc. - These attributes of Jehovah ought to inspire His afflicted people with confidence.
no searching of his understanding - therefore thy cause cannot, as thou sayest, escape His notice; though much in His ways is unsearchable, He cannot err (Job 11:7-9). He is never “faint” or “weary” with having the countless wants of His people ever before Him to attend to.