D&C 63:17 Wherefore, I, the Lord, have said that the fearful, and the unbelieving, and all liars, and whosoever loveth and maketh a lie, and the whoremonger, and the sorcerer, shall have their part in that lake which burneth with fire and brimstone, which is the second death.
will immediately inspire someone to interject that we are not to judge others.
Ironically, nobody seems to object that we are judging if we state that someone will be saved. Which is interesting, because if stating that a deceased person will be damned is breaking the commandment to "not judge", then stating that the same person would be saved would also be breaking the commandment to "not judge".
The Lord says that judgment is his. This is often applied by people in ways that directly contradict the scriptures. One wrong way to apply this is to use it to preach against citing what God has taught about his own judgement. The truth is that when we preach or apply God's own teachings about his judgement, we are not taking judgment from him, we are leaving it with him. We are simply exercising faith in his own promises. We are commanded to have faith in his promises, and that includes his promises about how he will judge. We see that faith exercised in the scriptures.
Alma 28:11 And the bodies of many thousands are laid low in the earth, while the bodies of many thousands are moldering in heaps upon the face of the earth; yea, and many thousands are mourning for the loss of their kindred, because they have reason to fear, according to the promises of the Lord, that they are consigned to a state of endless wo.
12 While many thousands of others truly mourn for the loss of their kindred, yet they rejoice and exult in the hope, and even know, according to the promises of the Lord, that they are raised to dwell at the right hand of God, in a state of never-ending happiness.
13 And thus we see how great the inequality of man is because of sin and transgression, and the power of the devil, which comes by the cunning plans which he hath devised to ensnare the hearts of men.
14 And thus we see the great call of diligence of men to labor in the vineyards of the Lord; and thus we see the great reason of sorrow, and also of rejoicing—sorrow because of death and destruction among men, and joy because of the light of Christ unto life.
First off, here we see in the scriptures many faithful members of the church who "truly mourn for the loss of their kindred, yet they rejoice and exult in the hope, and even know, according to the promises of the Lord, that they are raised to dwell at the right hand of God, in a state of never-ending happiness."
This is said without the merest hint of condemnation. These people are clearly "judging" the souls of their beloved departed. They know that they will be saved. But that judgement is described with whole hearted approval because that judgement is made by the word of the Lord. Apparently when we "judge" using the word of the Lord as our measuring stick, we are not taking judgement from the Lord, merely having faith in his promises and thereby echoing his own judgement. It is therefore not wrong, but met in this scripture with frank approbation.
There are many others who "have reason to fear, according to the promises of the Lord, that they are consigned to a state of endless wo."
Here again, we see judging in the scriptures. But that "judging" isn't condemned at all. It is judging "according to the promises of the Lord". There is no suggestion here that there is something wrong with "fearing, according to the promises of the Lord, that they are consigned to a state of endless wo". We are not taking judgement from him, apparently, when we simply apply his own promises about what his judgement will be. In these scriptures that appears to be the case even with the final judgement.
The issue appears to be the same one we see in Alma 11.
Alma 11:35 Now Zeezrom said unto the people: See that ye remember these things; for he said there is but one God; yet he saith that the Son of God shall come, but he shall not save his people—as though he had authority to command God.
36 Now Amulek saith again unto him: Behold thou hast lied, for thou sayest that I spake as though I had authority to command God because I said he shall not save his people in their sins.
37 And I say unto you again that he cannot save them in their sins; for I cannot deny his word, and he hath said that no unclean thing can inherit the kingdom of heaven; therefore, how can ye be saved, except ye inherit the kingdom of heaven? Therefore, ye cannot be saved in your sins.
The issue here is whether Alma and Amulek had authority to say that certain people wouldn't be saved. The claim is that saying so is "commanding God". But Amulek's response is that there is no sense in which he is commanding God if he simply takes God's own words about what he will do as being true.
We can judge by the scriptures what is right and wrong. We have seen examples in the Book of Mormon of many people correctly judging someone's final reward by the promises God has made. Amulek states that to assert that God will stick to his words in determining who to save is not commanding God. Put differently, it is not taking judgement from God, it is simply exercising faith in his own words. It is simply exercising faith in what God has stated that his judgement will be.
And you cannot have faith in what God has said he will do and offend God by doing so.
The same applies when judging right and wrong. In fact, not only can we judge right and wrong using the promises of the Lord, it is imperative that we do so.