(So they called their companion, and he dared [to do it]...)

(So they called) – meaning, after We sent the she-camel and they maintained this system of sharing [the water], they grew weary of that and resolved to hamstring the she-camel. (So they called) to hamstring it, their companion, (who was Qudar ibn Salif, the red one of Thamud, and he was the boldest of them).

(So he dared [to do it]) – meaning, he emboldened himself to undertake it despite its enormity, without concern for it.

(So he hamstrung [it]) – meaning, he brought about the hamstringing of the she-camel. It is permissible that what is meant is: he dared [to approach] the she-camel and hamstrung it; or, he dared [to take up] the sword and killed it. In any case, the object of "dared" is omitted, and the consequential connection (tafri’) is perfectly sound.

It has been said: "dared" is treated as an intransitive verb, meaning he brought about the essence of daring, and the Almighty’s saying (So he hamstrung) is an explanation of it, not a consequence of it; however, the weakness of this view is not hidden.

"Daring" (al-ta’ati) is generally the act of taking/attempting, as is understood from the speech of more than one scholar; some have added the qualification "with effort/exertion."

The attribution of the hamstringing to them in the Almighty’s saying (So they hamstrung the she-camel) is because they were satisfied with it.