فَلَمْ تَقْتُلُوهُمْ وَلَكِنَّ اللَّهَ قَتَلَهُمْ وَمَا رَمَيْتَ إِذْ رَمَيْتَ وَلَكِنَّ اللَّهَ رَمَى وَلِيُبْلِيَ الْمُؤْمِنِينَ مِنْهُ بَلَاءً حَسَنًا إِنَّ اللَّهَ سَمِيعٌ عَلِيمٌ ﴿۱۷﴾ ذَلِكُمْ وَأَنَّ اللَّهَ مُوهِنُ كَيْدِ الْكَافِرِينَ ﴿۱۸﴾ إِنْ تَسْتَفْتِحُوا فَقَدْ جَاءَكُمُ الْفَتْحُ وَإِنْ تَنْتَهُوا فَهُوَ خَيْرٌ لَكُمْ وَإِنْ تَعُودُوا نَعُدْ وَلَنْ تُغْنِيَ عَنْكُمْ فِئَتُكُمْ شَيْئًا وَلَوْ كَثُرَتْ وَأَنَّ اللَّهَ مَعَ الْمُؤْمِنِينَ ﴿۱۹﴾

﴾17﴿ Falam taqtuloohum wa laakinnal laaha qatalahum; wa maa ramaita iz ramaita wa laakinnal laaha ramaa; wa liyubliyal mu'mineena minhu balaaa'an hasanaa; innal laaha Samee'un Aleem
﴾18﴿ Zaalikum wa annal laaha moohinu kaidil kaafireen
﴾19﴿ In tastaftihoo faqad jaaa'akumul fathu wa in tantahoo fahuwa khairul lakum wa in ta'oodoo na'ud wa lan tughniya 'ankum fi'atukum shai'anw wa law kasurat wa annal laaha ma'al mu'mineen

﴾17﴿ So you did not kill them, but Allah killed them, and you did not make the pebbles reach the eyes of the disbelievers when you threw them from your fist, but Allah made them reach their eyes (and did this) And that He may grant the believers from Himself a goodly gift. Indeed, Allah is All-Hearing, All-Knowing
﴾18﴿ This is indeed what happened (and know that) Indeed, Allah, the Exalted, weakens the plot of the disbelievers
﴾19﴿ If you had sought a decision, then indeed the decision has come to you. But if you desist, then that is better for you. And if you return to fighting, then We will return the help to the believers And let not your group of people prevent you from your duty, even if they are many. Indeed, Allah is with the Muslims

[17] This is the sixth reason for the first claim. The summary is that those polytheists were killed in Badr, or stones struck their eyes—but you did not do it; rather, Allah the Exalted did it. And through this, spoils were attained—so do not dispute over them.
"Wa lakinna Allah qatalahum" (But it was Allah who killed them): This attribution is due to the fact that Allah granted the believers the ability and success to kill the disbelievers despite their limited means.
Another explanation is that the killing was done through the angels, as some narrations state that a Companion had not yet struck when the head of the disbeliever fell.
Question: In this verse, the act of throwing (ramy) is both attributed to the Prophet (May Allah bless him and give him peace) and also negated from him—how can this be explained?
Answer: The attribution of ramy to the Prophet is from the outward/visible perspective, as the Prophet (May Allah bless him and give him peace) took a handful of pebbles and threw them toward the disbelievers.
The negation of ramy means that the act of causing the pebbles to reach the eyes of every disbeliever was not the Prophet's doing—that was the work of Allah the Exalted, as it was a miracle.
Benefit: The act that is within the will and effort of the servant—like physically throwing the pebbles—is attributed to the Prophet with "idh ramayta" (when you threw). But the act that is beyond human ability—like making each pebble hit its target—is negated from the Prophet and attributed to Allah.
Question: Why is the outward aspect of killing not attributed to the believers, like it was done with ramy?
Answer: Because the true meaning of killing here is the taking of the soul, which happens after the action of the killer, and this part is attributed solely to Allah the Exalted. As for the part within the servant’s capability—like using the tools of killing—that can also be called "killing," but that’s not the intended meaning here.
[18] This address is to the believers, and in "dhalikum" (that is for you), there is a reference back to "balā’an ḥasanan" (a good trial/blessing).
There is a hidden subject (mubtadā'), meaning: “The purpose is that—dhalikum (that is for you)”.
The phrase "wa-anna" is either coordinated (connected by wa) to "dhalikum", or "i‘lamū" (know) is implied and omitted.
[19] This is a warning and intimidation, and the address is to the disbelievers—though at the end, there is good news for the believers.
The summary is that the disbelievers had made a supplication, and Allah the Exalted turned the evil outcome of that very supplication against them, defeated them, and caused them to be overcome.
There are two interpretations of this verse:
1. First interpretation: The address is to the disbelievers. This is the preferred explanation, because the final statements in the verse support it.
2. Second interpretation: The address is to the believers. The commentators have written that Abu Jahl and his companions, before setting out for Badr, held the cover of the Ka‘bah and made this supplication: “O Allah, whichever of these two groups is on guidance and is more beloved to You, grant them victory.” But both qualities—guidance and being beloved to Allah—were present in the believers, so Allah accepted that supplication in favor of the believers.
Before "wa-anna Allah", the phrase "wa‘lamū" (know) is implied but omitted.
And this portion of the verse is a glad tiding to the believers of divine, special help.