Ibn Qayyim al-Jawziyyah cited many of the lessons derived from the battle of Uhud, among them:
1. The believers learned the negative consequence of disobedience, loss of courage and dispute, and that what occurred was the result of it. As Allāh said:
And Allāh had certainly fulfilled His promise to you when you were killing the enemy by His permission until [the time] when you lost courage and fell to disputing about the order [given by the Prophet] and disobeyed after He had shown you that which you love. Among you are some who desire this world, and among you are some who desire the Hereafter. Then he turned you back from them [defeated] that He might test you. And He has already forgiven you, and Allāh is the possessor of bounty for the believers. [3:152]
When they experienced the consequence of their disobedience to the Messenger ﷺ, their weakening and their arguments, they became more careful and aware thereafter.
2. Allāh’s wisdom and method required that His messengers and their followers triumphed at times and are defeated at times, but the outcome was always in their favour. Because if they were continually victorious, kuffar as well as believers would join them, so believers could not be distinguished from others.
3. Sincere believers were distinguished from munafiqeen, for when Allāh gave the Muslims victory over their enemies on the day of Badr some entered Islam whose motives were not as they appeared. So, the wisdom of Allāh necessitated a test to differentiate between the believer and the munafiq. In this battle, the munafiqeen showed their true colours and spoke of what they had previously concealed. So, the believers realized that they had an enemy from within and thus could be cautious of them and prepared for them.
4. Allāh tests His servants in both good times and bad through that which they like and which they dislike, in victory and defeat. When they show firm obedience and servitude in what they like and what they dislike, then they are true servants of His.
5. If Allāh had always given them victory in every circumstance and had always subdued their enemies, they would have become oppressive and arrogant. His servants are only kept righteous and balanced through good times and bad, hardship and ease.
6. When Allāh afflicts them with setbacks, loss and defeat, they become humble and submissive, making them deserving of His might and victory.
7. Allāh has prepared for His believing servants positions in His Jannah which they cannot reach through their deeds; they will reach them only through difficulties and trials. So, He gives them the means to reach those positions in the form of problems and ordeals.
8. When enjoying continuous health, wealth and ascendancy, human souls acquire an oppressive and impatient nature. This is a disease that hinders one on his journey to Allāh and the Hereafter. So, when Allāh intends to honour a soul, He gives it difficulties and hardships which serve as treatment for that disease, like a doctor who makes a patient drink a bitter medicine or removes diseased parts from him. And if he left him to his own wishes and inclinations, they would destroy him.
9. Martyrdom in the sight of Allāh is among the highest ranks earned by His allies. The Shuhada are His privileged servants who are nearest to Him. In fact, after the rank of Siddeeq comes that of the shaheed. The only way to attain this rank is through the circumstances leading to it, i.e., being overcome by an enemy.
10. When Allāh intends to destroy His enemies he provides them with the causes of their destruction. The greatest of these causes after unbelief is their oppression, tyranny and abuse of His sincere allies, their waging war against them and overpowering them. In this way, He purifies His servants of their sins and faults. And thereby, He increases the causes of His enemies’ destruction.
Reference : Zad al-Ma`ad