﴿ وَمَكَرُوا۟ مَكْرًۭا وَمَكَرْنَا مَكْرًۭا وَهُمْ لَا يَشْعُرُونَ ﴾

“And so they devised an evil scheme; but We devised a subtle scheme (of Our own), and they perceived it not.”

(So they plotted a plot) they planned to kill Salih and all those who believed with him: (and We plotted a plot) and We wanted to kill them, (while they perceived not) Our plotting; it is also said that this means: the angels killed them in the house of Salih by hailing stones at them without them perceiving it.