Psalms 127:4

As arrows [are] in the hand of a mighty man,.... Are shot out with great strength; come with much force, and do execution, and do not return in vain; with which men defend themselves, and annoy their enemies; see Jeremiah 50:9;

so [are] children of the youth: not young children, or children in their youth; but such who are born to their parents when they are in their youth; and which are generally healthful and strong, and their parents live to see them grown up; and who are useful to protect them, and defend their persons and properties from enemies when grown old and feeble, and unable to defend themselves: whereas children born to them in old age are generally unhealthy and weak; and besides, their parents rarely live to see them brought up, or to be helpful to them. So Christ's spiritual seed and offspring, who are the dew of his youth, are strong, and overcome the evil one; and are serviceable in the defence of his cause and interest.