Know… before whom you are destined to give a judgment and accounting.
Ethics of the Fathers, 3:1
Said Rabbi Israel Baal Shem Tov: When a person comes before the supernal court to account for his sojourn on earth, he is first asked to voice his opinion on another life. “What do you think,” he is asked, “about one who has done so and so?” After he offers his verdict, it is demonstrated to him how these deeds and circumstances parallel those of his own life. Ultimately, it is the person himself who passes judgment on his own failings and achievements.
This explains the peculiar wording of the above passage of the Ethics, “before whom you are destined to give a judgment and accounting.” Is not the verdict handed down after the cross-examination of the defendant? So should not the “judgment” follow the “accounting”? And why are you destined to “give judgment” as opposed to being judged? But no judgment is ever passed on a person from above. Only after he has himself ruled on any given deed does the heavenly court make him account for a matching episode in his own life.
The same idea is also implicit in another passage in our chapter of the Ethics: “Retribution is extracted from a person, with his knowledge and without his knowledge.” As a person knowingly expresses his opinion on a certain matter, he is unwittingly passing judgment on himself.
What we have here is a most profound insight into the specialty of the human soul. In all of creation, nothing is loftier than the “spark of G-dliness” that is the soul of man. This is reflected in the fact that man has been given the power of choice—a power he shares only with the Creator Himself.
Free choice allows him to stumble and err, but it is also what makes his potential for good infinitely greater than G-d’s more spiritual creations. So even when a soul comes to stand in judgment, implying that there are perhaps faults and failings in its past performance, no judge, be it the loftiest and most spiritual of heavenly beings, has any jurisdiction over its fate. The only power on earth or heaven that can judge man is man himself.
From an address by the Rebbe, Shevat 10, 5720 (February 8, 1960)
Adapted from the teachings of the Rebbe by Yanki Tauber
 Cf. Nathan’s admonishment of King David, Samuel II 12.
 Ethics of the Fathers, 3:16
 See 2nd chapter of Tanya