﴿ فَجَعَلْنَٰهُمْ سَلَفًۭا وَمَثَلًۭا لِّلْءَاخِرِينَ ﴾

“and so We made them a thing of the past, and an example to those who would come after them.”

And We made them a thing past salaf is the plural of sālif similar in pattern to khādim khadam that is to say a precedent as a lesson and an example for others after them that they posterity might take their predicament as a lesson and so not engage in actions similar to theirs.