Matthew Henry Commentary Psalms 129:5-8

"Let them be put to shame and turned backward, All they that hate Zion. Let them be as the grass upon the housetops, Which withereth before it groweth up; Wherewith the reaper filleth not his hand, Nor he that bindeth sheaves his bosom. Neither do they that go by say, The blessing of Jehovah be upon you; We bless you in the name of Jehovah." — Psalms 129:5-8 (ASV)

While God's people will flourish like the loaded palm tree or the green and fruitful olive, their enemies will wither like the grass upon the housetops (for in eastern countries, housetops are flat, and what grows there never ripens); so it is with the designs of God's enemies. No wise man will pray the Lord to bless these mowers or reapers. And when we remember how Jesus rose and reigns, and how His people have been supported, like the burning but unconsumed bush, we will not fear.