10 And thus commandeth the Father that I should say unto you: At that day when the Gentiles shall sin against my gospel, and shall reject the fulness of my gospel, and shall be lifted up in the pride of their hearts above all nations, and above all the people of the whole earth, and shall be filled with all manner of lyings, and of deceits, and of mischiefs, and all manner of hypocrisy, and murders, and priestcrafts, and whoredoms, and of secret abominations; and if they shall do all those things, and shall reject the fulness of my gospel, behold, saith the Father, I will bring the fulness of my gospel from among them.
11 And then will I remember my covenant which I have made unto my people, O house of Israel, and I will bring my gospel unto them.
12 And I will show unto thee, O house of Israel, that the Gentiles shall not have power over you; but I will remember my covenant unto you, O house of Israel, and ye shall come unto the knowledge of the fulness of my gospel.
(3 Nephi 16:10-12)
We deal with temporary injustices all the time, some of them very long-lasting, but temporary nonetheless. People who are unkind and dishonest prosper, while people who are generous and trustworthy are penalized. That temporary imbalance is an important characteristic of mortal life, because it gives us time to repent and opportunities to exercise our faith.
Though the mills of God grind slowly;
Yet they grind exceeding small;
Though with patience he stands waiting,
With exactness grinds he all.
(“Retribution,” in The Belfry of Bruges and Other Poems, collected in 1870 Longfellow Poems (1960 edition), 331).