The law of Restoration requires that the Lord will reward mercy with mercy, and justice with justice. Therefore, if we want to be judged with fairness and mercy at the last day, then we must judge with fairness and mercy in mortality. On this subject, someone will usually quote, judge not that ye be not judged (Matt 7:1). This means that we should not be judgmental. However, in the world we live in, we are required to appropriately pass judgment all the time. The bishop passes judgment on ward members. All parents pass judgment on the behavior of their children and do it on a regular basis. Business and work decisions require judgment and fairness. This is why the Joseph Smith Translation alters this verse as follows, judge not unrighteously, that ye be not judged: but judge righteous judgment
The Lord doesn’t expect us to live a life without ever passing judgment. He is the Great Judge and we are to emulate him in all things—including righteous judgment. This concept is encapsulated in the word of the Lord to the 12 disciples in the New World, know ye that ye shall be judges of this people, according to the judgment which I shall give unto you, which shall be just. Therefore, what manner of men ought ye to be? Verily I say unto you, even as I am (3 Nephi 27:27). Therefore, the phrase, judge not that ye be not judged, is impractical. The more correct statement is that we should judge righteous judgment. Certainly, this must be done with the utmost care and wisdom. Otherwise we may find ourselves concerned with another’s mote at the expense of our own beam, For with what judgment ye judge, ye shall be judged: and with what measure ye mete, it shall be measured to you again (Matt 7:2).