«اِلنَّارْ تِخَلِّفْ رُمَادْ»

The image is of a strong blaze that burns out and leaves nothing behind except cold, grey residue. The saying applies this to families: a person of real worth and generosity may still produce a son or daughter who carries none of that brilliance, only something dull and spent.

The force of the proverb rests on a pun. The colloquial verb for leaving something behind is also used for having children, a double sense English cannot hold at once. So the fire both leaves ash and fathers it, turning a natural observation into a remark about disappointing heirs.

Said when a generous, honorable person's child turns out foolish or mean-spirited, as a rueful or sharp comparison. It can wound if applied to a real family in their hearing, so it is best kept for commentary rather than addressed to those concerned.