But what says he of them? The next words are, "Let them be even as the grass of the house tops: that withers before it be plucked up" [Psalm 129:6]. The grass of the house tops is that which grows on house tops, on a tiled roof: it is seen on high, and has not a root. How much better would it be if it grew lower, and how much more joyfully would it bloom? As it is, it rises higher to a quicker withering. It has not yet been plucked up, yet has it withered: not yet have they received sentence from the judgment of God, and already they have not the sap of bloom. Observe their works, and see that they have withered....The reapers will come, but they fill not their sheaves from these. For the reapers will come, and will gather the wheat into the barn, and will bind the tares together, and cast them into the fire. Thus also is the grass of the house tops cleared off, and whatever is plucked from it, is thrown into the fire; because it had withered even before it was plucked up. The reaper fills not his hands thence. His next words are, "Whereof the reaper fills not his hand; neither he that binds up the sheaves his bosom" [Psalm 129:7]. And, "the reapers are the angels," [Matthew 13:39] the Lord says.
[AD 430] Augustine of Hippo on Psalms 129:6-7