Tafsir of Qaf 50:14

And the companions of the thicket (Ashab al-Aykah): It is said: they were a people to whom Shu‘ayb, peace be upon him, was sent, distinct from the people of Madyan. They inhabited an aykah—which is a dense thicket of trees—and were named after it.

And the people of Tubba‘: The Himyarite. He was a believer, while his people were disbelievers; hence, he was not condemned, whereas his people were. A full discussion regarding what is in this verse has already preceded in [the surahs of] al-Hijr, al-Dukhan, and al-Furqan.

"Each denied the messengers": That is, regarding the religious laws with which they were sent, among which is the Resurrection, upon which they all unanimously agreed. This means that each group of those mentioned denied their messenger, or that all of them together denied all the messengers. The singular pronoun in the word "each" (kull) refers to the totality, or [it means that] each one of them denied all the messengers, because the messengers were in agreement regarding the call to monotheism and the warning of Resurrection and Gathering; therefore, denying one of them is a denial of all.

The intent behind the totality (kulliyah) is [to denote] multiplicity, as in His, the Exalted’s saying: "And she has been given of all things." Otherwise, indeed, some from the people of Nuh believed, as did others. Furthermore, what has been mentioned [about Tubba‘] is evident based on the assumption of his prophethood; then, based on the assumption of its absence—which is the opinion of the majority—the meaning of his people denying the messengers, peace be upon them, is their denial of the preceding messengers who were united upon monotheism and the Resurrection, and it was to that which Tubba‘ was calling them.

"So My threat was justly incurred": That is, My threat became necessary and fell upon them, and it is the sentence of punishment.