Let them be as the grass upon the housetops - The housetops, or roofs of houses, covered with sand or earth, in which seeds of grass may germinate and begin to grow, but where, as there is no depth of earth, and as the heat of the sun there would be intense, it would soon wither away. See the notes at Isaiah 37:27.
Which withereth afore it groweth up - This, even if it has any meaning, is not the meaning of the original. The idea in the Hebrew is - and it is so rendered in the Septuagint, the Latin Vulgate, and by Luther - "which before (one) pulls it, withers." Grass would wither or dry up, of course, if it were pulled up or cut down, but the grass here spoken of withers even before this is done. It has no depth of earth to sustain it; having sprouted, and begun to grow, it soon dies - a perfect image of feebleness and desolation; of hopes begun only to be disappointed. "This morning" (says Dr. Thomson, "Land and the Book," vol. ii., p. 574) "I saw a striking illustration of this most expressive figure. To obtain a good view of the Tyropean, my guide took me to the top of a house on the brow of Zion, and the grass which had grown over the roof during the rainy season was now entirely withered and perfectly dry."

As the grass upon the housetops - As in the east the roofs of the houses were flat, seeds of various kinds falling upon them would naturally vegetate, though in an imperfect way; and, because of the want of proper nourishment, would necessarily dry and wither away. If grass, the mower cannot make hay of it; if corn, the reaper cannot make a sheaf of it. Let the Babylonians be like such herbage - good for nothing, and come to nothing.
Withereth afore it groweth up - Before שלק shalak, it is unsheathed; i.e., before it ears, or comes to seed.

(c) Let them be as the grass [upon] the housetops, which withereth afore it groweth up:
(c) The enemies who lift themselves high, and as it were approach the Sun, are consumed with the heat of God's wrath, because they are not grounded in godly humility.

Let them be as the grass upon the housetops,.... The tops of the houses in Judea were flat, and so grass grew upon them, being covered with plaster of terrace; though it was but small and weak, and being on high was exposed to the scorching sun, and soon withered (b); and Menochius says (c) he saw such roofs in the island of Corsica, flat, and having earth upon them, smoothed and pressed, on which grass grew of its own accord; but being burnt up in summertime by the sun, soon withered, as here said. But what Olaus Magnus (d) relates is somewhat extraordinary; that, in the northern Gothic countries, they feed their cattle on the tops of houses, especially in a time of siege; he describes their houses as built of stone, high and large, and covered with rafters of fir and bark of birch; upon which is laid grass earth, cut out of the fields foursquare, and sowed with barley or oats, so that their roofs look like green meadows; and that what is sown, and the grass that grows thereon, might not wither before plucked up, they very constantly and diligently water it; but in the eastern countries, which are hot, and have but little rain, grass could not retain its verdure long, as follows;
which withereth afore it groweth up; to any height, the usual height of grass: or, "before it is plucked up", as the Septuagint, Vulgate Latin, and Arabic versions; and so Jarchi. And this was their usual way of gathering in their corn; and which continues to this day, as Mr. Maundrell (e) affirms, who was an eyewitness to it in many places; where they plucked it up by handfuls from the roots, leaving the most fruitful fields as naked as if nothing had grown on them; and this they did for the sake of the straw, which was generally very short, and necessary for the sustenance of cattle; to which he thinks there is here a manifest allusion; but not corn, but grass, is here spoken of. The Targum is,
"before it flourisheth, an east wind cometh, blows upon it, and it is withered;''
and to the same purpose the Syriac version,
"which when the wind comes upon it, it fades and withers.''
This expresses the high and elevated state and condition of wicked men, the pride and haughtiness of their hearts; yet their weakness and frailty, and the danger they are exposed unto, through the wrath and vengeance of God upon them; when they consume and wither away like grass on the housetops, and never come to the happiness they are hoping and wishing for; see Isaiah 37:27.
(b) See Shaw's Travels, p. 210, 211. (c) De Republica Hebrews. l. 7. c. 5. p. 666. (d) De Ritu Gent. Septent. l. 9. c. 12. (e) Journey from Aleppo to Jerusalem, p. 144. Ed. 7.

The poet illustrates the fate that overtakes them by means of a picture borrowed from Isaiah and worked up (Psalm 37:27): they become like "grass of the housetops," etc. שׁ is a relative to יבשׁ (quod exarescit), and קדמת, priusquam, is Hebraized after מן־קדמת דּנה in Daniel 6:11, or מקּדמת דּנה in Ezra 5:11. שׁלף elsewhere has the signification "to draw forth" of a sword, shoe, or arrow, which is followed by the lxx, Theodotion, and the Quinta: πρὸ τοῦ ἐκσπασθῆναι, before it is plucked. But side by side with the ἐκσπασθῆναι of the lxx we also find the reading exanthee'sai; and in this sense Jerome renders (statim ut) viruerit, Symmachus ἐκκαυλῆσαι (to shoot into a stalk), Aquila ἀνέθαλεν, the Sexta ἐκστερεῶσαι (to attain to full solidity). The Targum paraphrases שׁלף in both senses: to shoot up and to pluck off. The former signification, after which Venema interprets: antequam se evaginet vel evaginetur, i.e., antequam e vaginulis suis se evolvat et succrescat, is also advocated by Parchon, Kimchi, and Aben-Ezra. In the same sense von Ortenberg conjectures שׁחלף. Since the grass of the house-tops or roofs, if one wishes to pull it up, can be pulled up just as well when it is withered as when it is green, and since it is the most natural thing to take חציר as the subject to שׁלף, we decide in favour of the intransitive signification, "to put itself forth, to develope, shoot forth into ear." The roof-grass withers before it has put forth ears of blossoms, just because it has no deep root, and therefore cannot stand against the heat of the sun.
(Note: So, too, Geiger in the Deutsche Morgenlndische Zeitschrift, xiv. 278f., according to whom Arab. slf (šlf) occurs in Saadia and Abu-Said in the signification "to be in the first maturity, to blossom," - a sense שׁלף may also have here; cf. the Talmudic שׁלופפי used of unripe dates that are still in blossom.)
The poet pursues the figure of the grass of the house-tops still further. The encompassing lap or bosom (κόλπος) is called elsewhere חצן (Isaiah 49:22; Nehemiah 5:13); here it is חצן, like the Arabic ḥiḍn (diminutive ḥoḍein), of the same root with מחוז, a creek, in Psalm 107:30. The enemies of Israel are as grass upon the house-tops, which is not garnered in; their life closes with sure destruction, the germ of which they (without any need for any rooting out) carry within themselves. The observation of Knapp, that any Western poet would have left off with Psalm 129:6, is based upon the error that Psalm 129:7-8 are an idle embellishment. The greeting addressed to the reapers in Psalm 129:8 is taken from life; it is not denied even to heathen reapers. Similarly Boaz (Ruth 2:4) greets them with "Jahve be with you," and receivers the counter-salutation, "Jahve bless thee." Here it is the passers-by who call out to those who are harvesting: The blessing (בּרכּת) of Jahve happen to you (אליכם,
(Note: Here and there עליכם is found as an error of the copyist. The Hebrew Psalter, Basel 1547, 12mo, notes it as a various reading.)
as in the Aaronitish blessing), and (since "we bless you in the name of Jahve" would be a purposeless excess of politeness in the mouth of the same speakers) receive in their turn the counter-salutation: We bless you in the name of Jahve. As a contrast it follows that there is before the righteous a garnering in of that which they have sown amidst the exchange of joyful benedictory greetings.

House - tops - Which there were flat. Which - Having no deep root, never comes to maturity. And so all their designs shall be abortive.