Al-Anfaal 8:42

[Remember] when you were on the near side of the valley [of Badr], and they were on the far side, and the caravan was on the lower ground beneath you. If you had made prior arrangements to encounter, you would have failed to keep that appointment. But [it happened] so that Allah might accomplish what had already been decreed, and so that those who chose to perish would perish after seeing clear evidence, and those who chose to survive would survive after seeing clear evidence. Indeed, Allah is All-Hearing, All-Knowing.

[Remember] when you were on the near side of the valley, and they were on the farther side, and the caravan was lower [in position] than you. If you had made an appointment [to meet], you would have missed the appointment. But [it was] so that Allāh might accomplish a matter already destined - that those who perished [through disbelief] would perish upon evidence and those who lived [in faith] would live upon evidence; and indeed, Allāh is Hearing and Knowing.

42. (And remember) when you (the Muslim army) were on the near side of the valley, and they on the farther side, and the caravan on the ground lower than you. Even if you had made a mutual appointment to meet, you would certainly have failed in the appointment, but (you met) that Allâh might accomplish a matter already ordained (in His Knowledge), so that those who were to be destroyed (for their rejecting the Faith) might be destroyed after a clear evidence, and those who were to live (i.e. believers) might live after a clear evidence. And surely, Allâh is All-Hearer, All-Knower.

When ye were on the near bank (of the valley) and they were on the yonder bank, and the caravan was below you (on the coast plain). And had ye trysted to meet one another ye surely would have failed to keep the tryst, but (it happened, as it did, without the forethought of either of you) that Allah might conclude a thing that must be done; that he who perished (on that day) might perish by a clear proof (of His Sovereignty) and he who survived might survive by a clear proof (of His Sovereignty). Lo! Allah in truth is Hearer, Knower.