אַֽל־תִּשְׂמְחִ֤י פְלֶ֙שֶׁת֙ כֻּלֵּ֔ךְ כִּ֥י נִשְׁבַּ֖ר שֵׁ֣בֶט מַכֵּ֑ךְ כִּֽי־מִשֹּׁ֤רֶשׁ נָחָשׁ֙ יֵ֣צֵא צֶ֔פַע וּפִרְי֖וֹ שָׂרָ֥ף מְעוֹפֵֽף׃
"Terre des Philistins, ne te réjouis pas sans mesure de ce qu’elle soit brisée, la verge qui te frappait; car de la racine d’un serpent sortira un basilic, et son fruit sera un dragon volant.
Siftei Chakhamim
That consume. Meaning that השרפים ["the consuming"] is a description of the snakes that are mentioned in the verse, meaning “the snakes that consume.” Not that this was a species of snake such as שרף מעופף ["a flying seraph" (Yeshayahu 14:29)] or נחש שרף ועקרב ["snake, saraph and scorpion" (Devarim 8:15)]. For if this were so the verse should have said והשרפים ["and the seraphim"]. [One might ask:] It is written, (v. 8) “Make yourself a שרף ["consuming snake"]” which implies that it was a species of snake called the saraph. The answer is that it means “make for yourself a consuming snake” for we find something similar [that an adjective implies a subject that is not stated explicitly in the verse] where מאכלו בריא ["his food is healthy"] (Chabakuk 1:16), refers to a healthy sheep.
Ibn Ezra
והצפיעות And the issue. The female children are perhaps meant; comp. יצא צפע shall come forth a cockatrice (14:29).29According to this remark צפע means offspring, but in commenting on 14:29 he says that צפעני ═ צפע means cockatrice, and is more dangerous than נחש serpent. A joke at the expense of women is perhaps intended by this remark. The real reason for this explanation is very likely to be found in the masculine and feminine terminations of the two words צאצאים and צפיעות. Since he is said to be the father, the men of Judah are as it were his sons, and the women his daughters. All vessels of small quantity. The children are compared to small vessels.