‘(The case of the litigation is that,) this is my brother. He has ninety nine ewes (female sheep) while I have one ewe; still he says, “Make it over to me,” and he has been prevailing by his arguments upon me.’ (38:23)

Commentary
NUMBER 99: The story which is contained in this verse and which is actually found in verses 21 to 26 of this chapter speak about an important event in the life of Prophet Dāwūd. 
Two brothers who had a dispute made their way into the house of Prophet Dāwūd - albeit through impermissible means by scaling the walls of his palace and barging in on him. They had an argument with one another and as Prophet Dāwūd was known to be fair in his rulings, they sought adjudication from him and asked him to provide them religious guidance.
What were these two brothers fighting over? Just like many disputes which come up between people, it was about money. The plaintiff who was petitioning his case to Prophet Dāwūd told the judge that the defendant, his brother, had 99 female sheep while he had only one female sheep and his brother who had significantly more even wanted to take the one possession that his brother had!
From this verse it seems that the defendant was able to over-power the plaintiff and take away that one female sheep and so now they were coming to Prophet Dāwūd seek arbitration and a fair judgement from him.
Rather than waiting for the defendant to present his arguments and his side of the story, the Quran tells us that Dāwūd immediately passed judgement. Although he was correct in his verdict, however justice and fairness dictated that he listen to both sides and then offer the ruling. 
He told the defendant that he had been unjust in his dealings with the plaintiff and that he had no right to ask for the one female sheep. He made an interesting point which even runs true today with business partners that:
وَإِنَّ كَثِيرٗا مِّنَ ٱلۡخُلَطَآءِ لَيَبۡغِي بَعۡضُهُمۡ عَلَىٰ بَعۡضٍ إِلَّا ٱلَّذِينَ ءَامَنُواْ وَعَمِلُواْ ٱلصَّٰلِحَٰتِ وَقَلِيلٞ مَّا هُمۡۗ 
…And indeed, many associates oppress one another, except for those who believe and do righteous deeds - and few are they… (38:24)
Prophet Dāwūd realized his quickness in passing judgement and the test he was under by Allah and so submitted to his Creator, asked for forgiveness and turned back to Him in repentance for this act – even though it was NOT a sin that he committed. 
Allah forgave him, and confirmed that Dāwūd still has a closeness to Himself and that He ensured that Dāwūd would be given a great place in paradise with the blessings of that world. 
Point of Reflection
In our personal lives, whether at school, work, in the community or in our family setting, we must always ensure that when disputes arise, we listen to all of the sides and are not quick in making any conclusions on others and must remember that there is One who is the Best of Judges who will soon pass judgement on us.