Ver. 2. To know what was in thine heart— Man's life is a state of probation. The wanderings of the children of Israel in the wilderness afford us a lively resemblance of the human pilgrimage through this world. God, who knows the hearts of all men, needs not to be informed how they are disposed towards him. The expression here, to know what was in thine heart, must therefore be understood after the manner of men; and the meaning is, that God did as men usually do when they want to try any one's sincerity; i.e. he laid opportunities in their way of giving unexceptionable proof of their integrity; a discovery, which, though of no signification with respect to God, was yet very useful to themselves, and instructive to others. Nothing tries the heart so much as adversity, and perhaps nothing is so useful to it. It is finely said by Seneca, "If you have not been an unhappy man, I am sure you are so: if you have travelled the stage of life without the opportunity of encountering an adversary, nobody can know what your strength is; no, not even yourself."
Related Commentaries of Deuteronomy 8:2
Deuteronomy 8:2
2 And thou shalt remember all the way which the LORD thy God led thee these forty years in the wilderness, to humble thee, and to prove thee, to know what was in thine heart, whether thou wouldest keep his commandments, or no.