Translation:

12. That We might make it a message unto you and that ears (that should hear the tale and) retain its memory should bear its (lessons) in remembrance.

Notes (Tafseer)

5646. It was a memorial for all time, to show that evil meets with its punishment, but the good are saved by the mercy of Allah.

5647. Cf. the biblical Phrase, "He that hath ears to hear, let him hear" (Matt. xi. 15). But the phrase used here has a more complicated import. An ear may hear, but for want of will in the hearer the hearer may not wish, for the future or for all time, to retain the memory of the lessons he had heard, even though for the time being he was impressed by it. The penetration of the truth has to be far deeper and subtler, and this is desired here.