In these verses the psalmist pictures the destruction of the enemies in terms of the grass and weeds which grew wild on the flat roofs of the houses, roofs made of branches or reeds with mud spread over them. The hot sun and scorching wind would kill the growth before it reached maturity (see similar language in 37.2; 103.15-16). The verb translated grows up can be taken to mean “pull up”; so “which withers before it is pulled up” (Biblia Dios Habla Hoy, New Jerusalem Bible, Bible en français courant). Given the uncertainty of the meaning of the Hebrew text, Oesterley and Weiser change it to read “grass … which the east wind withers” (see New Jerusalem Bible footnote), but this does not seem necessary. The picture of grass sprouting on a house top will make little sense in some areas. Biblia Dios Habla Hoy says “weeds that grow on the roof tiles.” It may be more satisfactory to say “like grass that grows where there is not enough soil for its roots.” It may be necessary in some cases to supply an illustration or a note.

Reaping is described in verse 7: the reaper held the stalks of grain in one hand and cut them with the scythe which he held in the other hand; then he would hold the stalks against his chest while tying them up in a sheaf. The psalmist is saying in verse 7 that the grass that grows on housetops is not cut and tied up, because it is of no value. This is the fate he wishes on the enemies of Israel. In many languages it will be necessary to make the connections between verse 7 and verse 6 clearer by saying, for example, “reapers who gather up stalks of grain and tie them in bundles do not gather up the worthless weeds that grow on the roof of a house.”

Quoted with permission from Bratcher, Robert G. and Reyburn, William D. A Handbook on the Book of Psalms. (UBS Helps for Translators). New York: UBS, 1991. For this and other handbooks for translators see here .