Charles H. Spurgeon on Psalms 109:9

Let his children be fatherless. Helpless and shiftless. A sore vexation to many on their death beds, and just enough upon graceless persecutors. But happy are they who, when they lie dying, can say as Luther did, "Domine Deus gratias ago tibi quod velueris me esse pauperem, et mendicum, &c. Lord God, I thank thee for my present poverty, but future hopes. I have not an house, lands, possessions, or monies to leave behind me. Thou hast given me wife and children; behold, I return them back to thee, and beseech thee to nourish them, teach them, keep them safe, as hitherto thou hast done, O thou father of the fatherless, and judge of widows." —John Trapp.

Verses 9-10, 12-13. "His children; ""his posterity." Though in matters of a civil or judicial character, we have it upon the highest authority that the children are not to be made accountable for the fathers, nor the fathers for the children, but every transgressor is to bear the penalty of his own sin; yet, in a moral, and in a social and spiritual sense, it is impossible that the fathers should eat sour grapes, and yet that the children's teeth should not be set on edge. The offspring of the profligate and the prodigal may, and often do, avoid the specific vices of the parent; but rarely, if ever, do they escape the evil consequences of those vices. And this reaction cannot be prevented, until it shall please God first to unmake and then to remodel his whole intelligent creation. —T. Dale, in a Sermon to Heads of Families, 1839.

Verses 9-13. Under the Old Covenant, calamity, extending from father to son, was the meed of transgression; prosperity, vice versa, of obedience: (see Solomon's prayer, 2Ch 6:23): and these prayers of the psalmist (cf. Ps 10:13, 12:1 58:10, etc.) may express the wish that God's providential government of his people should be asserted in the chastisement of the enemy of God and man. —Speaker's Commentary.