Lehi, after having read the book, exclaimed, "Great and marvelous are thy works, O Lord God Almighty!" He realized the power of God. But also his justice, goodness and mercy. And therefore his heart was filled with joy, notwithstanding his sympathy with the people. In the vision it became clear to him, as it would be to all who can see "the end from the beginning" that the goodness and mercy of God are best served by his justice. And therefore his heart was filled with joy. (See Rev. 19:1-3)