Why did Prophet Muhammad raid caravans in Medina?

One of the claims frequently made by anti-Muslim websites is that after Prophet Muhammad emigrated to Medina, he became a warlord and launched offensive wars against the tribes around him for worldly gains. The truth is that the Meccan aristocracy had been violently intolerant of the new religion from the very beginning. The Muslims were forced to take up arms in defense of their right to practice Islam.
After the Prophet fled to Medina following 13 years of persecution, the Quraysh issued an ultimatum to the leadership of Medina that they must kill the Prophet or face war. They wrote to Medina saying:

إِنَّكُمْ آوَيْتُمْ صَاحِبَنَا وَإِنَّا نُقْسِمُ بِاللَّهِ لَتُقَاتِلُنَّهُ أَوْ لَتُخْرِجُنَّهُ أَوْ لَنَسِيرَنَّ إِلَيْكُمْ بِأَجْمَعِنَا حَتَّى نَقْتُلَ مُقَاتِلَتَكُمْ وَنَسْتَبِيحَ نِسَاءَكُمْ

You have given protection to our companion. We swear by Allah that you must fight him or exile him, or else we will come at you in full force. We will kill your fighting men and take your women.

This tradition was declared authentic by Al-Albani in Ṣaḥīḥ Abī Dāwūd 3004.

The Meccans were not content to let the Muslims worship in peace. Sa’d ibn Mu’adh, one of the Prophet’s companions, went to Mecca to perform his pilgrimage at the sacred mosque. While he was there, Abu Jahl, one of the leaders of Mecca, issued an open threat:

أَلاَ أَرَاكَ تَطُوفُ بِمَكَّةَ آمِنًا وَقَدْ أَوَيْتُمُ الصُّبَاةَ وَزَعَمْتُمْ أَنَّكُمْ تَنْصُرُونَهُمْ وَتُعِينُونَهُمْ، أَمَا وَاللَّهِ لَوْلاَ أَنَّكَ مَعَ أَبِي صَفْوَانَ مَا رَجَعْتَ إِلَى أَهْلِكَ سَالِمًا‏

I see you going around Mecca securely while you have given protection to a heretic. I imagine you are supporting and helping him. By Allah, if you were not in the company of Abu Sufyan, I would not let you safely return to your family!

In other words, if Sa’d had not been under the protection of Abu Sufyan, a powerful tribal leader, then Abu Jahl would have had him killed.

In this context, Allah revealed a verse allowing the Muslims to defend themselves after having required them to be patiently endure up to this point.

Allah said:

أُذِنَ لِلَّذِينَ يُقَاتَلُونَ بِأَنَّهُمْ ظُلِمُوا ۚ وَإِنَّ اللَّهَ عَلَىٰ نَصْرِهِمْ لَقَدِيرٌ الَّذِينَ أُخْرِجُوا مِن دِيَارِهِم بِغَيْرِ حَقٍّ إِلَّا أَن يَقُولُوا رَبُّنَا اللَّهُ

Permission to fight has been given to those who are being fought, because they were wronged. Verily, Allah is able to give them victory. They are those who have been evicted from their homes without right and only because they say: Our Lord is Allah.

Surat al-Hajj 22:39

This verse makes clear that the reason the Muslims were allowed to fight was because they had been driven out and violently oppressed only because of their religion. As the Meccans were preparing for war, the Muslims prepared to launch raids on their caravans as a means to disrupt their economic war-making capabilities. What is more, the Meccans had confiscated the property that the Muslims had left behind and were taking it to Syria to be sold for war funds.

Despite suffering this persecution, the Prophet commanded the Muslims to adhere to the highest standard of conduct and he prohibited them from plundering the enemy’s wealth.

عَنْ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ أَنَّهُ نَهَى عَنْ النُّهْبَةِ وَالْمُثْلَةِ

The Prophet, peace and blessings be upon him, prohibited plundering and mutilation.

The Prophet declared that the one who plunders, robs, and loots people is not a true Muslim.

Abu Huraira reported: The Messenger of Allah, peace and blessings be upon him, said:

وَلَا يَسْرِقُ حِينَ يَسْرِقُ وَهُوَ مُؤْمِنٌ وَلَا يَنْتَهِبُ نُهْبَةً يَرْفَعُ النَّاسُ إِلَيْهِ فِيهَا أَبْصَارَهُمْ حِينَ يَنْتَهِبُهَا وَهُوَ مُؤْمِنٌ

The thief is not a believer while he is stealing. The plunderer is not a believer while he is plundering and the people are watching him.

Imran ibn Hussein reported: The Messenger of Allah, peace and blessings be upon him, said:

مَنْ انْتَهَبَ نُهْبَةً فَلَيْسَ مِنَّا

Whoever plunders the wealth of others is not one of us.

In another narration, the Prophet said:

وَمَنْ انْتَهَبَ نُهْبَةً مَشْهُورَةً فَلَيْسَ مِنَّا

Whoever is notorious for plunder is not one of us.

On one occasion, the Prophet saw that some of his companions had looted the enemy’s sheep. He commanded them to return the property to their owners.

Tha’labah ibn Hakam reported: We came across some sheep of the enemy, so we plundered them and set up our cooking pots. The Prophet passed by and ordered that they be overturned. The Prophet, peace and blessings be upon him, said:

إِنَّ النُّهْبَةَ لَا تَحِلُّ

As mentioned in the verse, permission was given to fight back only as a response to aggression. Muslims are allowed to fight for the right to practice Islam and to defend innocent people from oppression. No other motives are permissible, especially not to fight for worldly gains and spoils.

Abu Huraira reported: A man said, “O Messenger of Allah, a man intends to fight for the sake of Allah and he is seeking worldly gains.” The Messenger of Allah, peace and blessings be upon him, said:

 لَا أَجْرَ لَهُ

There is no reward for him.

The people found that very difficult and they said, “Return to the Messenger of Allah, for perhaps he did not understand you.” The man returned and he said, “O Messenger of Allah, a man intends to fight for the sake of Allah and he is seeking worldly gain.” The Prophet said:

لَا أَجْرَ لَهُ

There is no reward for him.

Then he returned a third time and the Prophet said:

لَا أَجْرَ لَهُ

There is no reward for him.

Nevertheless, the collection of spoils is an incidental consequence of war. The Prophet would collect the spoils and distribute them equitably among the community as charity. Moreover, the Prophet forbade Muslims from killing non-combatants and civilians, and he commanded them to behave magnanimously with the enemy.

Anas ibn Malik reported: The Messenger of Allah, peace and blessings be upon him, said to his army:

انْطَلِقُوا بِاسْمِ اللَّهِ وَبِاللَّهِ وَعَلَى مِلَّةِ رَسُولِ اللَّهِ وَلَا تَقْتُلُوا شَيْخًا فَانِيًا وَلَا طِفْلًا وَلَا صَغِيرًا وَلَا امْرَأَةً وَلَا تَغُلُّوا وَضُمُّوا غَنَائِمَكُمْ وَأَصْلِحُوا وَأَحْسِنُوا إِنَّ اللَّهَ يُحِبُّ الْمُحْسِنِينَ

Go forward in the name of Allah, with Allah, and upon the religion of the Messenger of Allah. Do not kill the elderly, children, young people, or women. Do not steal from the spoils but collect them, and behave righteously and in the best manner. Verily, Allah loves those who behave in the best way.

To conclude, the Prophet launched raids against the Meccan caravans in response to their declaration of war. The raids were meant to obstruct the Meccan’s plans to attack the new community in Medina. Even so, the Prophet prohibited his companions from stealing from the enemy and he told his army to behave honorably with them.