בַּת־עַמִּ֤י חִגְרִי־שָׂק֙ וְהִתְפַּלְּשִׁ֣י בָאֵ֔פֶר אֵ֤בֶל יָחִיד֙ עֲשִׂ֣י לָ֔ךְ מִסְפַּ֖ד תַּמְרוּרִ֑ים כִּ֣י פִתְאֹ֔ם יָבֹ֥א הַשֹּׁדֵ֖ד עָלֵֽינוּ׃
Fille de mon peuple! Ceins-toi d’un cilice, roule-toi dans la cendre, organisa un deuil comme pour un fils unique, d’amères complaintes; car soudainement l’envahisseur fondra sur nous.
Kitzur Ba'al HaTurim
ויהי השמש "And it was the sun" in the tradition. Here and elsewhere "and it was the sun" comes [in the context of destruction]. Corresponding to the two Temples, as it is written (Jeremiah 6:26), "And I will set your suns [i.e. Temple courtyards] and your gates for destruction."
Rashbam
the construction ovad is similar to mispad in מספד תמרורים in Jeremiah 6,26, where instead of misped we find mispad, just as here we find ovad instead of oved. Genesis 30,37 makal instead of makel, is another example of such a construction. The reason for the patach instead of the tzeyreh is that in each instance listed the noun is in a construct mode. A fourth example of such a construction is found in Leviticus 27,32 ma-assar bakar vatzon, instead of ma-asser bakar vatzon.
Chizkuni
מקל, “rod;” the letter ק has the vowel patach under it (instead of tzeyreh). This is not unusual for the construct mode; we find it also in the word מעשר, Leviticus 27,32, as well as in the word מספד in Jeremiah 6,26 which has the vowel patach under the letter .פ