(So, when you meet those who disbelieve (in battle), smite their necks) which means, `when you fight against them, cut them down totally with your swords.'
حَتَّى إِذَآ أَثْخَنتُمُوهُمْ
(until you have fully defeated them,) meaning, `you have killed and utterly destroyed them.'
فَشُدُّواْ الْوَثَاقَ
(tighten their bonds.) `This is referring to the prisoners of war whom you have captured. Later on, after the war ends and the conflict has ceased, you have a choice in regard to the captives: You may either act graciously toward them by setting them free without charge, or free them for a ransom that you require from them.' It appears that this Ayah was revealed after the battle of Badr. At that time, Allah reproached the believers for sparing many of the enemy's soldiers, and holding too many captives in order to take ransom from them. So He said then:
وَيُدْخِلُهُمُ الْجَنَّةَ عَرَّفَهَا لَهُمْ (and will admit them to the Paradise He has identified for them. - 47:6). This is the third bounty of Allah. He will not only admit them into Paradise but will identify for them the gardens of bliss and will make them familiar with such bounties as houris and mansions in a way that it would seem to them that they have been living there since eternity. If such an acquaintance was not made, Paradise would have seemed a strange world. It would have taken them time to find their abode, to accustom themselves with the new environment, and they would not overcome the sense of unfamiliarity for a period of time.
Abu Hurayrah ؓ reports that the Messenger of Allah ﷺ said: "By Him who sent me with the religion of Truth! As you are closely familiar with your wives and homes in this world, so you will know your abode and your wives of Paradise - rather even better. Some reports of Hadith tell us that an angel will be appointed for every single inmate of Paradise who will introduce them to their abode and wives in Paradise. Allah knows best.
Tazkirul Quran
Maulana Wahiduddin KhanOn ayahs 6–10
Here, disbelievers or rejectors refers to those who did not embrace the Faith despite compelling arguments having been put forward in its favour. Moreover, they unjustifiably waged war against the Prophet Muhammad and thus compelled the Prophet to take defensive steps. As regards such people, it has been ordained that in case of confrontation with them, they should be fought against and crushed, so that they should not be able to place impediments in the way of the mission of Truth. It has ever been the rule of God that those who rejected their Prophet would be destroyed after the conclusion of arguments. But in case of the last prophet, it was the will of God that, through him and his companions, the age of polytheism should be brought to an end and a new era of history should be brought into existence on the strength of the oneness of God. For this, epoch-making men were needed and their selection could be done only under the most trying circumstances: this purpose was achieved by sending the companions of the Prophet of God into the war waged by his opponents. Paradise is the most familiar and best known concept for a believer. He not only hears about it from the Prophet, but also, by means of his developed inner knowledge (ma‘rifah), gains an intuitive understanding of it. It is still this deep understanding of the unseen, hidden Paradise that inspires and encourages man to seek it, regardless of the sacrifices to be made. Had it not been so, nobody would have sacrificed today’s world in the hopes of entering tomorrow’s Paradise.
Uthmani text of the Madinah mushaf (King Fahd Complex). Translation: Saheeh International. Tafsir via Quran.com.