We are not left without proof of spiritual things. The justice of eternal law demands that the gospel be properly taught if men are going to be damned for refusing to accept and live it.
Evidence of the truthfulness of the gospel must be such that there could be no justification for unbelief upon the day of judgment. Thus Nephi testifies that God “proveth all his words.”
Malachi, in teaching the law of tithing, quotes the Lord thus:
“Prove me now herewith, saith the Lord of hosts [and in principle this applies to all his commandments, not just to the law of tithing], if I will not open you the windows of heaven, and pour you out a blessing, that there shall not be room enough to receive it”
Similarly, the Apostle Paul declared: “Prove all things,” and then “hold fast that which is good” (1 Thessalonians 5:21).
To those of our day the Lord has given the Book of Mormon,
“proving to the world that the holy scriptures are true, and that God does inspire men and call them to his holy work in this age and generation, as well as in generations of old; thereby showing that he is the same God yesterday, today, and forever.”