2 Samuel 14:7

the whole family, &c. The whole clan demanded blood-revenge, according to the primitive custom, sanctioned and regulated by the Mosaic Law. See Numbers 35:19; Deuteronomy 19:12-13.

and we will destroy the heir also The woman puts these words that we may kill him … and destroy the heir also into the mouth of her kinsmen, in order to make their conduct appear in the worst possible light, as actuated not so much by a wish to observe the law as by covetousness and a desire to share the inheritance among themselves. Cp. Matthew 21:38.

they shall quench my coal which is left The surviving son, who is the last hope for the continuance of his family, is compared to the live coal still left among the embers, by which the fire almost extinct may be rekindled.