Tafsir of Ad-Dhariyat 51:10

That is, the liars among those who hold conflicting opinions. The root of the word al-khars (conjecture/guessing) is speculation and estimation. It was then used metaphorically to mean lying, because it is, in most cases, the source of it.

Al-Raghib said: The reality of this is that every statement made based on speculation and estimation is called khars, whether it happens to conform to the reality of the thing or contradicts it, in the sense that the speaker did not say it based on knowledge, a dominant probability, or reported tradition. Rather, he relied in it upon speculation and estimation, like the act of the one who estimates the yield of fruit. Anyone who makes a statement in this manner may be called a liar, even if their statement happens to conform to what is being reported, as in His, the Almighty’s, saying: "When the hypocrites come to you..." (up to the end of the verse).

There is some discussion regarding this. The literal meaning of qutila (killed/slain) is well-known, but what is intended by it here is an invocation of destruction against them, regardless of the literal meaning.

It has been narrated from Ibn Abbas that he interpreted it as "cursed." Ibn al-Anbari said: "It is only interpreted as 'cursed' here because he whom Allah, the Almighty, curses is in the position of one who is killed and destroyed."

It was also recited: Qutila al-kharrasun (in the nominative case), meaning: "May Allah kill the conjecture-mongers."