Tafsir of Ash-Shu`ara' 26:173

(Meaning: A type of rain that was unprecedented, for it was stones of Sijjil, as stated explicitly in His saying—Exalted is He: "And when Our command came, We made their highest part their lowest, and We rained upon them stones of Sijjil." The combination of the two occurrences was to increase their humiliation. It has been said that the overturning (al-i’tifak) was for one group, and the raining was for another among them. According to what has been narrated from Muqatil, this was for those who were outside the city for some of their needs; this is perhaps what Qatadah intended by "the stragglers" (al-shudhdhadh) in what has been narrated from him.)

"So evil is the rain of those who were warned."

(The lam in [the word "al-mundharin"] is for the generic category (al-jins), and by this, it is possible for the genitive construction (al-mudaf ilayh) to be the agent of sa'a [evil/bad], based on the understanding that it carries the meaning of bi'sa [how evil is]. The object of censure (al-makhsus bil-dhamm) is omitted, and it is their rain. If sa'a is not interpreted in this manner, it is permissible for the lam to be for the purpose of reference (al-'ahd).)