Psalms 137:9

Blessed is he who shall take hold of and dash your little ones against the rock. The "little ones" are said to be thoughts. For example: I have seen a woman, I have desired her: at once, if I do not cut off that desire, and, as it were, take it by the foot and dash it against the rock while the desire is small, it cannot afterwards be cut off when it has grown. Blessed, then, is he who cuts it off at once, and dashes it against the rock. And the Rock is Christ.

And see then also how the Spirit counselleth thee, saying, "Dash the children of Babylon upon the stones while they are young." And well hath the word of prophecy called these passions "children", that it might show thee their powerlessness, and might encourage thee to victory; and it did not say "thy children," that it might not cause thee disgrace, as if such children appeared from thee, but it named them "children of Babylon," that is to say, children who were born of slavery and not of freedom, because the mother which giveth birth to lusts is the slavery which the word of prophecy hath symbolized by Babylon which hath been wasted, and which carrieth off rapaciously like spoil the power of the spiritual man, and plundereth his riches.

"Happy shall he be that repayeth thee, as thou hast served us." What repayment meaneth he? Herewith the Psalm closeth, "Happy, that taketh and dasheth thy little ones against the rock" (ver. 9). Her he calleth unhappy, but him happy who payeth her as she hath served us. Do we ask, what reward? This is the repayment. For what hath that Babylon done to us? We have already sung in another Psalm, "The words of the wicked have prevailed against us." For when we were born, the confusion of this world found us, and choked us while yet infants with the empty notions of divers errors. The infant that is born destined to be a citizen of Jerusalem, and in God's predestination already a citizen, but meanwhile a prisoner for a time, when learneth he to love ought, save what his parents have whispered into his ears? They teach him and train him in avarice, robbery, daily lying, the worship of divers idols and devils, the unlawful remedies of enchantments and amulets. What shall one yet an infant do, a tender soul, observing what its elders do, save follow that which it seeth them doing. Babylon then has persecuted us when little, but God hath given us when grown up knowledge of ourselves, that we should not follow the errors of our parents. ...How shall they repay her? As she hath served us. Let her little ones be choked in turn: yea let her little ones in turn be dashed, and die. What are the little ones of Babylon? Evil desires at their birth. For there are, who have to fight with inveterate lusts. When lust is born, before evil habit giveth it strength against thee, when lust is little, by no means let it gain the strength of evil habit; when it is little, dash it. But thou fearest, lest though dashed it die not; "Dash it against the Rock; and that Rock is Christ."